@KindyCat for exactly the same reason as Gender Change. The "For parodies (e.g. female ranma saotome) the change itself does not have to be shown." ruling that validates Gender Change on genderbends where the transformation isn't visible has been copied onto Gender Morph since the tag was created.
@Glovelove. Uh, no. For Gender morph, the change has to be at least IMPLIED. this isn't the case here. This is why Gender Change apply, but not Gender Morph.