This is an issue that's been going around in my twitter microcosm lately...the idea that males and females just move and gesture differently. And therefore, if you feel you don't have time to include females more than one gender as playable characters in your game, you're justified because of all the 'extra work' it would take.
I think that reasoning is BS, but I don't have an issue with the idea itself. If you want to give the girls "girly" movements and the boys "boyish" movements just for the heck of it, go for it. It's whatevs.
What I do have an issue with is people who think the idea is representative of objective reality. 9_9 I actually saw someone argue that women just "don't" sit the way men do. Like, they just "don't". Not even that they can't (which would be weird, but at least you could try to justify that) but that they somehow only ever consider sitting in 'womanly' ways.
I would like to hold myself up as an example of that being patently false, assuming that 'womanly' ways of sitting is just code for 'legs crossed' or something. Even when I wear skirts, I don't bother with that (if I can get away with it). And honestly, I don't even think it's a thing in the culture I come from; none of the women in my family or their friends sit according to Western etiquette. They tend to sit however they feel like. =/
In conclusion, three points:
= Everything is relative, even gender norms, so assuming every man or woman on earth is just 'predisposed' to act the way they do in your social environment is just setting yourself up for foolishness. In this day and age, the fact that your worldview is limited is not a legitimate excuse.
=People are all different anyway! I'm sure there are as many flamboyant guys as there are stoic gals, regardless of their gender identities. If anything, I'd think character-specific animation would be more of an issue: people with different personalities actually DO tend to move differently.
=If you're making a purely fictional game, you have the freedom to have your male/female characters move however you want. So maybe if you just don't want to do something, be honest and say that instead of pretending it's 'not possible'. ._.