I get that. And, I'm not unsympathetic. The only problem is, we all understand what is actually meant here, so, instead of quibbling over the words, either suggest a better terminology, or just let the terminology stand because it's right there in the definition that it's not supposed to be an elevation of one over the others but simply a spectrum of playstyles from simpler to more complicated. (Dammit, it really is HARD to find words that differentiate without sounding judgemental.

)
The problem is that you're looking for a terminology that says that one is a better form of the other -- that it is more. So, more dimensions is clearly better than fewer dimensions, so this terminology fits your conception that roleplaying has an arc of worse to better. I reject this concept outright. There are different ways to roleplay that achieve different goals. Playacting for entertainment purposes, for instance, is very valid and I engage in it often, but it's not superior to not playacting. It serves a different
goal.
To express this, I find there's a big difference between expressing a character and exploring a character. In D&D, the overwhelming mode of play is expression of character -- when you roleplay here, it's more to present a characterization and set of tropes. D&D focuses play on the party as the unit of interest, so building a character here has to align itself to this group identity first and foremost which leaves little room for exploration of the character and encourages just expression of some character. Even the BIFTs are on the lines of expression -- things you do but that don't cause any questioning of who the character actually is at any given moment. The zeitgeist expectations for this characterization have grown, such that now there's the idea that you'll at least do some playacting, but at no point has the idea that you're exploring this character to find out who they are caught on in any popular way. The levels of "but it's what my character would do" are still very shallow and often considered gauche if they conflict with the group identity. This is fine, though, and I very much enjoy this and engage with it -- I'm doing so now where I have a tiefling literally raised by his devil father who, nevertheless, is well-adjusted enough to adventure with the other misfits in the group and treat them as valued family even when expressing rivalries. This is expression of character.
On the other hand, you can have exploration of character. Here you're playing to find out who this character is, at least in some way. Individuals are important, even at the expense of the group -- characters can actively work against each other, even. In this mode, I'm looking to find things out about my character, so I need to risk my character in ways that do this. The mechanics may tell me that my character has changed -- such as when my Blades character stressed out of a scene and had a trauma applied. I learned something about my character here that I didn't invent. This isn't better than the above -- it's different, aimed at achieving a different objective.
And, both of the above can be accomplished quite fine with the video's description of dimension.