Right, but does that mean that pull-ups are part of the essence of masculinity?
The main attack against "sexism" is that it's essentialist, it holds that even if a woman can do 20 pull-ups, even if she has her gonads changed, she'll never "truly" be a man, there are irreproducible properties to maleness and femaleness that are natural and determinative.
The problems are that no one ever lays down a marker and say what these properties exactly are, because just about everything a man can do, a woman can do, and many other man cannot do. I can't do 20 perfect form pull-ups either, but that doesn't mean I'm not a man or any less of a man. And then essences break down completely when we deal with the case of hermaphrodites, or transsexuals, or queer people who decline either identification, or people that identify in some way at variance with their chromosomal sex. In the end the best we can come up with when it comes to sexual essence is chromosomes, but if that's all it is, or even if all it was was pull-ups, aren't these really irrelevant to things like "damsel tropes," or male gaze, or sexual fetishization? And then, even when it is relevant, it's a naturalistic fallacy to assert that because women are X, a depiction of them as X in a video game is justified. That's an appeal to nature to settle question of aesthetics or morality.
I'm not disagreeing with your position, a lot of feminists agree with your basic point (though they'd take issue with your presentation). I'm just pointing out that the question is irrelevant for the most part and is probably intractable, due to its reliance on a metaphysical worldview that's disputed.