Original creators are wrong
The team behind the original animated series addressed the backlash referring to Morph as a nonbinary mutant saying the word “nonbinary” is the same as the word “shapeshifter, which is Morphs power.
https://www.cbr.com/morph-creators-x-men-97-backlash
Nope. That’s total BS. Mystique is a shapeshifter too but didn’t identify as nonbinary.
Nonbinary refers specifically to someone who feels they aren’t one gender.
Has nothing to do with having the ability to shift from one to the other.