This seems like the ultimate manifestation of old adage "there are no girls on the internet." I suspect that females (especially those not in the tech industry) tend to overwhelmingly hold accounts in their real name, whereas the vast majority of pseudonymous posters are men. It makes a lot of sense from a social conditioning perspective of communication: that females tend to be more relationship-focused whereas males tend to be more object-focused.

As a result, for girls, getting misgendered under a pseudonymous account is seen as danger that comes with the territory. And of course they take it in stride, because that's just what women do all the time.