I always wondered about this pool with characters like mokou who already are in the extra stage, boost them up to powers like this and wouldn't that make an already EX character phantasm stage material? then theres Yukari who's phantasm to begin with and theres nothing greater then that so far in the touhou universe so boosting her to a new level wouldn't have a name.
Eh I'm thinking to much again. Badass stuff like this and having a brain isn't good for me.
The "Extra Stage girls" pool is for Touhou characters who have been visibly altered into a "powered up" form that's a significant change from their normal state. Something akin to EX-Keine in canon (as opposed to Kogasa, who shows up as an EX midboss with no change in appearance at all). Characters who are already EX are fine for the pool as long as they fit the stated criteria. Even Yukari, who's already Phantasm, has a post in this pool: post #650052