First, this thread is a mess, y'all have already pretty much dropped the original proposal related to 12D that's in the OP to discuss completely unrelated topics.
Second, the only agreement I could see from y'all is that "11D bad, we want higher" but there barely seems to be an agreement on how all these different things (Phases, Sephiroth, Dimensions, etc) work and how they're meant to scale in relation to each other and in relation to specific characters.
Third, the 12D argument is bad because espers use the "11th dimension" not the "eleventh spatial dimension", you'd need a statement saying exactly what the 2nd says to use the logic you're proposing for 12D (someone else had given a similar explanation in the first page, but whatever).
Fourth, the arguments for Curtana are also really bad (and someone legitimately used ChatGPT to create an argument? That's kinda sad, ngl) because, as others explained, "dimensions that can be expressed" doesn't mean "all numbers correspond to a dimension". I like this as much as y'all, I don't want 11D either, but if the statements are flawed they're flawed and that's it.
In the case of the Hidden Phase, it transcends the material world, dimensions, and all religious and mythological phases.
Give me a quote with that exact wording.
And although I don't particularly like discussing other universes, in Fate, even though only about 6-8 dimensions actually appear, just one character's line—"surpassed all dimensional theories"—grants the feat of transcending dimensions.
Give me a similar statement in Toaru.
Like, not just you, Piamma, but everyone here seems to miss the simple fact that the actual relationship between dimensions, phases and the Sephiroth has not been properly explained (I didn't read GT11 yet, NO spoilers).