um, there's no such thing as an actual Fairy Godmother full stop. It's all made up.
So maybe fairy godmother apprentices graduate to be fairy godfathers. Or maybe someone casts a spell at graduation and they become fairy godmothers, because while no real human can change sex really, imaginary magical people can absolutely change sex magically! Or maybe Godmother is an honoury title that men can also have in fairyland. Or maybe apprentices never progress to another role just like Santa's little helpers never become Santa. Or maybe all fairies are female even the ones with beards (like dwarves). Or maybe they have no concept of sex or gender and reproduce with acorns and moonlight.
Who knows? No one, because it's all made up.
I mean, I really am as gender critical as the next woman, I'm pretty sure I've proved that, and I care masively about the appropriation of female language for males, but even I think fairy tale characters can be allowed a bit of gender fluidity!
As long as Nick is not claiming to be a female person in real life and is safe to be with children (and whether or not I align with Disney's other brand values, I'm sure they do take safeguarding seriously so there's no reason to assume he's any less safe than his colleagues), good luck to him.