If you ask for a random sample I feel like you get a fairly even distribution of male/female/lgbtq, but sometimes yes you might get a sample that's all men or women or whatever. So yes it can be biased. It's the luck of the draw.

The good thing is you can just tell it the exact proportions you want, or even get it to just give you more variety. If you say "Give me 50/50" or "give me a table of all possibilities, then base it off an equal distribution" or simply "Wow, that's a lot of dudes/kind of stereotypical, can you give me more variety?" or even "This data set seems biased, can you give me suggestions for more variety". If you talk in dnd terms and go like '1dx table with the roles gender/sex/race/orientation' or whatever, it will do that, it'll even show you the dice rolls if you demand it.

So initial impressions can be biased...but your own brain is biased too. The good thing is you can generate a whole host of npcs literally in the time it takes you to roll a die 10 times lol. You can even tell it to combine disciplines by doing something like to literally combat it's own biases by adding in thoughts about DEI/representing other people if you want. Or you can go opposite and tell it to be 'conservative' if you wanna be like that.

Heck, you can even literally feed it what you posted here, and the ChatGPT will address your concerns and make a table accordingly.