I think the important difference between aziraphale and crowley’s relationship with gender is that like. aziraphale is simply agender. he likes presenting as male, but past that doesn’t really have a concept of gender in relation to his own identity. gender exists on a different plane of reality from which he has entirely separated himself. while crowley actively embraces the idea of gender nonconformity and deliberately uses the fact that he’s nonbinary to present however the hell he wants to. neither have a gender in the conventional human sense, but crowley has a much more involved relationship with the concept of gender exploration and presentation than aziraphale does, whose overall attitude is just like “whatever. I don’t even go here”
as @thevioletsunflower put it, and deserves to be shared with the world: Aziraphale’s gender is “heavens no”. Crowley’s gender is “Hell yes”