Shadowcatcher said
wait i have a crazy theory. think about yourself. you know what you look like head to toe right? well, most people do. if you look in the mirror while ingame, maybe its that you recognize its you then from that memory in your brain, the gear gets that image and turns it into your avatar.im not good at explaining, but do you see what im getting at. I dont have to look in a mirror to remember what i look like, however maybe the mirror actived something in your brain that made you think about your appearance. i said its crazy, but since we're throwing out theories, how about that one?
That's actually a really good theory... but the problem with it is the Homunculous (or however it's spelled) the diagram of the human body according to sensory perception... You do not TRULY register your body as you SEE it, but as you FEEL it. when rubbing something with your fingers, it always seems larger than when you see it (especially so when using a non-dominant hand) http://static.ddmcdn.com/gif/brain-homunculus-a.gif
So by that... if it's going off of memories scanned, then it could possible horribly eschew proportions.
Then if it's how you percieve yourself, what about people with phantom limb syndrome? or those who don't truly see their bodies as they physically are like some anorexic people? they feel and see things about their body that aren't truly there.
Then as for taking sexual identity from the mind... what about transgenders? They don't identify as the sex they physically are.
So the most plausible excuse for them having true gender data, is that the players had their own profiles on their headsets that have their RL information.