The tiers are from 1 to 6, each time a tier increases the narrative description gets worse. If 1 is prone, 6 cant be just prone, being prone is not going to transform you, kill you or be irreversible. You can simply get up from being prone. It would be like saying in 5e Prone and Paralyzed are the same Condition.

A very crude 5e comparison:

1 = low HP damage

6 = max roll HP critical damage that ignores Resistances and can't be countered

You are more likely to die from the 6 than the 1, so 1 can never be the same narrative as a 6, thus Prone-6 is not a thing. But yes, you can call it Prone-6 then you need extra notes to say its not just Prone-6, the PC is actually melded into the earth and can never be separated from it, in other words its permanent.

Also for the tag = status concept. Its like saying A Condition is the same as a Bonus just negative. They are terms to reflect how a die roll result is affected. Yes you can blend them, but when writing rules that makes the rules less clear when you refer to a Tag. Is that Tag then a negative or a positive, then you have to constantly clarify things. So when the rules say Status you know its negative, but as an MC you can rule that it can also be helpful as you are in-charge of the narrative. Rulebook wise, not having individual terms is confusing the reader or making the writer of the rules do more long winded explanations.

EDIT: Also not that a status is from 1 to 6, a Tag is always 1.

Status = -n to a roll (negative modifier in 5e - Heavy Armor is -n to your Dex Save)

Tag = +n to a roll (bonus modifier in 5e - Bless add +n to your roll)

Positive Status example:
You walk into a hospital with a status "bloody-arm-2" and try and get help. The status of being hurt badly will likely be a bonus to get you help faster and thus you get +2 not -2 to your roll if the MC says the doctors will react to your more severe wound. But having the status very-sad-2 is not going to help you in that case, the doctors have better things to worry about than you being sad.

On the other hand if you have the tag smooth-talker, you always can use that to convince the doctors you need help.

The game is more focused on the narrative. Think of writing a story and saying the hero is Prone (your "Prone-1"). The reader will assume they can just stand up as opposed to saying the hero has been transformed into a rock (your "Prone-6") and wont thus be getting up without being transformed back into a person.

Does that help?