Considering the fact that they're even making a move to lift restrictions on swimsuits from past summer events (according to the game's files) I think the ship has long sailed when it comes to the devs perspective on the removal of gender restrictions. We can speculate all we want that the devs did this out of obligation or felt resentful over it - it really doesn't matter anymore. It has become a key priority to remove gender restrictions on a huge batch of items every major patch and new glamours are launching without gender restrictions at all. Are there going to be some things that remain locked? Yes. Are some folks still going to complain? Yes. Is it still an undeniable truth that those pushing for neutrality have won? Absolutely.

Is there a reason they haven't released Hilda's hairstyle? Who knows. It probably isn't that they don't want to, but that's as viable an justification as any in the absence of a better one. It could be somewhere on some long list of requested features, it just hasn't been treated as a top priority by XIV's devs. Right now implementing the duty support system, expanding the Viera/Hrothgar hairstyle roster and lifting gender restrictions on gear are being given the biggest emphasis. As those projects reach their conclusion maybe we'll see Hilda's hair in an upcoming liveletter. Or not.