I wear a ponytail myself, as well as a beard. But I must say that if people claim to mistake your friend for a woman just because of hair length, then they are either mocking him or not paying attention! Men and women dress, stand and move quite differently, their body language is also different.

As for the 'my pronouns are..' thing, it's patronising. It assumes the reader is a halfwit at best. If the person in front of me dresses and behaves like a woman, the mere possession of a deep voice or an adams' apple is not going to make me use male pronouns!