Gender is smth neurological. That's why it's unchangeable: male and female brains are slightly different, and trans brains tend to align more with their experienced genders. Idk how that works with nbi people tbh. Genderfluids are something that I do understand as the brain activity in different areas, so it may be that some parts of the brain are more active, and thus more dominant and others are kind of dormant.
Oh, and I thought you were neko/poseidon. srry, I'm acoustic