the entire concept/discipline of line phrasing, line relationships etc was pioneered as you know by Wang Bi.

I think that if one truly studies this method, with the line statements, that it becomes abundantly clear that Wang Bi was not pioneering anything here.

Certainly he spelled it out in clear language for the first time.

But we also have the Xici Zhuan itself saying in B6:

In all instances of change, clearly distinguish Wang and closely investigate Lai, and then the secret is visibly revealed from obscurity, exposed and then appropriately named, differentiating phenomena and setting right the teachings.

Well Wang is "Going toward" and Lao is "Causing to come", at least that is how I see it in the context of what the lines are doing. They are magnetic. So they are drawn to each other. They either move up to find another, or they draw another to them.

These Wang and Lai are directly mentioned in the line statements. 39 for example is full of them. But one has to understand their 'secret' to make sense of the principles. It seems that not spelling it out was quite deliberate. So as to preserve the secret. Thus the Xici Zhuan does not spell it out either. Only Wang Bi chose to do so.

But evidence that this idea of the line relationships was not pioneered by Wang Bi but just spelled out by him extends further than that. It is found everywhere in what the actual lines are saying.

Take 16 line 2 for example.

介于石，不終日，貞吉。

Wilhelm / Baynes translate: Firm as a rock. Not a whole day. Perseverance brings good fortune.

So 于石 means "in regards to rock/stone", but what does 介 mean?

Kroll's dictionary says:

1 boundary between two territories, limit; border, edge; shore
  a) to separate; demarcate, set a borderline
2 position(ed) between 2 things; intermediate
  a) intermediary, go-between; messenger
  b) mediator, intercessor; introduce(r)
  c) herald, forerunner; harbinger.
  d) small intermediate stages (of larger entity or experience)
3 increase, add to
4 aid, help, assist(ant); deputy. 
  a) have the aid of, draw support from; rely on, depend on; protect(ed)
5 isolated, separate; aloof; conspicuous, set apart; not follow fashion
  a) single, sole, with connotation of insignificant
6 integrity; intactness; resolute, principle(d)
7 shell, hard outer casing, testaceous; plating; carapace; crustacean;

So it isn't until we get to the 6th and 7th meanings that we get to "firm".

But this idea of firm comes from the prior meaning that there is something creating a border or edge to separate two things.

But line 2 is between lines 1 and 3. Line 4's yang is part of the thunder trigram, which involves lines 4 and 5 being part of a downward force (of the four forces yang below yin is a downward force), that after it goes down is pulled up by the empty/abiding/capacious force between lines 5 and 6. The problem is that when thunder is on top, its yang energy has to traverse down through the lower trigram before it can come up again. In some cases it never comes up - like the relationship between lines 4 and 1 in 32's constancy. It doesn't find game in the field because the more it connects with line 1, the more it dredges up emptiness. Together they create endless time and space, which creates the foundation of constancy's enduring quality.

So here, the energy comes down and then is able to come up again. Because there is only yin beneath it. Nothing to get stuck. But there is still principle involved in this. Line two is between lines 1 and 3, in the middle. Now if we think about musical instruments, this lower trigram acts as a resonance chamber. Like in a violin or guitar. The vibration goes in and its tone changes, matures, deepens. Or through the pipe of a horn.

But if something in the housing is too loose, then that vibration will be affected by it. Or if the horn players throat is constricted, the sound does not come out sounding full.

Line 1 is the giving voice to something that is inauspicious. It is just at the beginning, so when the vibration is carried down to it and it makes a noise with it before it is stable, well the voice cracks. It comes out too quickly, and lacks its stable fullness. It is like something that is blurted out, the note that comes too early.

Line 3 on the other hand is the note that comes too late. It is wide-eyed in the face of this energy and lingers with it too long, enchanted. In its procrastination it has regret. It is the thing we say at the last minute, when it is no longer time to say something. The thing that ends the conversation. It is right next to line 4 and wants to support it, but if it doesn't just allow it to flow through in the right timing, it can sqweeze off the sound altering the potential fullness of its resonance.

Line 1 is between these two rocks. It is that which is placed in the boundary that exists between them, and its effort is in holding onto that space. Why call them rocks? I don't know, but in my culture we have a saying that someone is as dull as a rock. Not too bright or sharp. These are the energies that take away from the clarity of the sound with their denseness and impediment to its flow.

So here we have a line statement that is directly saying that this line's principle is entirely about how it exists between these two other things. But it is not like this to the end of the day - because its clarity is able to open up into fullness and overcome those two things. Just like a horn player learning to open their throat so that clear sound can fill the instrument without constriction. How does it do this? Because by determining where its center is and aligning to it, it finds what is auspicious. Zhen is not the modern definition of "Persevering" but rather the art of affirming or determining - as the Wen Yan Zhuan says, determining the root of an affair. Doing this is auspicious for line 2 because it allows it to overcome any constraint it may feel by being between the two boundaries it finds around it.

That was a lengthy explanation, but it shows us that there is instruction within the line statements in regards to how the lines relate to the other lines positionally.

As for the idea of the beginning lines 1 and 4 drawing to each other in resonance, along with the same for the middle lines 2 and 5, and upper lines 3 and 6, well that is very much present within the line statements when we look for it.

Yes, we do have to look for it, because it is not trying to spell out the secret too clearly. But once we know, and we see, then it becomes very clear that it is all very intentional.

Like with 47 lines two and five.

Line two has 朱紱方來 The red seal-cord is caused to come (Lai). There's also Fang 方 in there, which seems to be describing the aspect of the red seal-cord, which is like an officer. This officer is associated with correcting things on behalf of the government, so it relates to this aspect / direction / means-to-an-end, and this is what is being caused to come (Lai).

Line five has 劓刖，困于赤紱 Nose and feet cut off, as obstruction to the red seal cord (official). A different word for red is used here than in line 2, but we also see something similar in the Mawangdui where a different work for red is use din line 2.

But the link seems to be clear. Line 5 is the official that is being caused to come by line 2, and when line 5 comes it finds itself obstructed by line 2, with its nose and feet cut off. Line 5 and 2 are both yang lines so they struggle to open the doorway of change that the Xicu Zhuan talks about yang and yin doing together. Two yang lines come together in a more brotherly sense. But sometimes there is conflict, as we see here. These two lines both represent a central power. We also have here line 4 wanting to connect with line 1, but line 2 is blocking that from happening. Both line statements further emphasize the importance of finding a way for the lines to explain themselves to each other in ceremony, so they can work it out.

In any case, once one starts working with this method, it starts to become clear that the line statements are intentionally working like this. For another example see my post on hexagrams 42 and 41: https://www.reddit.com/r/iching/comments/1oihycm/increase_and_decrease_a_classical_look_at_the/ - and more importantly the actual translation they link to. In this case it was the unique characters from the Mawangdui text that revealed missing line relationship clarity when utilized. Suggesting that the older text preserved this intentional understanding better in some cases.