Sex does sell, however the problem here isn't that fact. Its your all or nothing single minded definition of what that entails. You also seem to think sex sells only refers to a scowling blonde into a metal bikini and not the truth of the situation. Such as that even just a moderately attractive girl working at a sales counter attracts more sales than a boy of the same age. You could always look this up.

Also while this game is not like those fighting games, I disagree with your idea that the blonde in the metal bikini is less serious than the shirtless He-man in the fur boxers. Inmost game the woman is probably ging to played as much if not more than the he-man is. And as for being taken seriously that all depends on her game mechanics, same as the little girl that shoots fire at you, or that green slime monster character.

You can argue against the facts all you want, but at this point your just stating opinions as facts and elevating semantics as victories.