When I was playing MMOs, I found many people were very surprised that I was a girl, playing a girl character, in a typically male class. The impression I got is that there's a fair amount of gender bending going on anyway and none of it necessarily has anything to do with Real life gender identity.
I know that when I play anything where I get to choose gender, appearance, etc. I'll tend to try to be something completely different from myself. To me, that's the point of a role-playing game. It's boring to role play someone as similar to yourself as possible. So I usually end up as a blue-skinned male sorcerer orc or something. Not because in real life I identify as male, or an orc, or blue, but just because it's a fun opportunity to make believe. I honestly think that a lot of the time, that's all it is, and it shouldn't be read into too much. That'd be like assuming that someone who is good at Risk
is a sociopathic dictator at heart or something. For a lot of us, it's just a game, and we take the opportunity to pretend because the point of a game is to be fun and not mundane. Seasoned players are generally aware of this.
So sure, a person might choose a female character because they identify as female, but they might also choose it because they identify as male and it's fun to play something different, no matter what their biological gender.
Also, the pedant in me wants to point out that biological gender and genetic gender (e.g. XX, XY, etc.) are not necessarily the same thing. Look it up on Wiki though because I'm sure it would be TMI for a lot of people here in a public forum.