It doesn't need to. Because any number of dimensions is generalized to be the same thing because they really are. If someone is beyond dimensions as a concept, Ultima isn't assuming that this universe with 5 physical dimensions has infinite others it has to transcend, it's just that it transcends dimensions as a physical extension. If we assume this is 6th-dimensional, then by pure logic we can say it's not really beyond dimensions, because we are just saying it becomes something akin to 6th-dimensional, when it goes against its quality. Giving something beyond a logical hierarchy something that is only an extension of said hierarchy is the same as saying it's not beyond that logical hierarchy, which is Ultima's point.
There are nuances to this, of course. There are a lot of franchises that do what I like to call "false metaphysics", which is when instead of something truly metaphysical, it's only an unknown extent of what is physical. Any work that puts stuff like Platonic forms with higher dimensions (Such as Morrison's DC works or all those religions that use pseudo-science to say stuff like "angels live in the 5th dimension" are like that). For those cases, they of course are just an extension of the physical instead of something truly metaphyisical, and Ultima isn't requesting to change that. He merely requests that works that don't use that kind of logic are forced to do so when that logic doesn't work when pushed to its most logical consequence.
In the end, it's not something focused on just pushing high tiers to any metaphysics reference or r>f usage, even though a lot of people looking forward to that thread just want an excuse to make a CRT giving their favorite verses 1-A ranting. It's merely about accepting a logical consequence of the nature of metaphysical and qualitative superiority to give a more faithful representation of works that do that kind of stuff.
Basically, think of it like saying that when Proclus explained infinite and eternity he was just saying stuff like "adding one higher dimension", when doing that would only expand the physical representation of what he wanted to transcend, instead of just giving the transcendence he was implying. In the end, it doesn't matter how complex any given physical system is, they are still physical and bounded by that logical hierarchy.
