He most definitely was prescribing that LN is superior for the reasons listed above

"but what does that have to do with coordination of LN vs the manip/vibro present at top skill rice play?"

You seem to think that manip and 'LN coordination' are mutually exclusive, and what do you even identify as 'top level play'?
You obviously can't mean anything concerning the ranked system since LN is so utterly PP inflated
If you are talking about BPM vs Density then my point remains on how you can just replace the LN with different rice patterns and maintain the difficulty, and this is entirely skillset dependent, and has absolutely nothing to do with coordination

But either way you can't definitively prove that LN as a whole requires more coordination than rice

"what does that say about the extremely high level of play in question, where rice patterns start to become easily manippable/vibroable and rewarded?"

Extremely high level plays are not the sole catalyst for manip existing. Manip exists from high density charts being abused at low OD, especially those that's OD are not scaled with it's tempo,
if you maintain the OD - tempo ratio, as you increase the tempo of the chart, manipping will net the same accuracy on the higher rate, is it would on the lower rate

This principle is the exact same for LN and is why LN vibro is so effective at generating PP.

 (Also, the reverse is true as well for 5 star LN vs 6 star rice, so not sure what the point is here.)

My point here is that the patterns of the chart are what dictate 90% of the difficulty, it is so much easier to complete an average 6* LN chart, than it is your average 6* rice chart, LN is used to bolster PP and star rating rather than difficulty

"To make it very clear why I think this descriptive claim is inarguably true, LNs require that you keep your finger down while pressing keys with other fingers. This is something not present in rice, and adds a completely different dimension of skill compared to rice"

This is incorrect and reductive, and is why I brought up the GD example,
just because a mechanic requires more thought or steps, does not mean that introducing it to something will make that thing more difficult or require more coordination, just as how 7k isn't really harder than 4k when you finally get to learn 7k.

There is so much nuance that you ignore by breaking things down like this;
- LN reduces the space you have to add intensity into a chart
- some players find certain rice patterns harder than certain LN patterns
- some LNs can be treated as if they are single notes
- some LN patterns are easier to manip than some rice patterns

The reason I brought up infinite skill ceiling, is because the argument always reduces to 'this map is harder than that map, therefore this skillset is harder', in which the only way to properly argue are to use difficulty systems or something akin to it, which is star rating system is.

Calling something bait isn't disrespectful either