What you've shown is that not all swaps are valid, but you haven't shown that this particular swap is invalid. The point of swapping the words is to illustrate

What you've shown is that not all swaps are valid, but you haven't shown that this particular swap is invalid. The point of swapping the words is to illustrate that generalizing about people based on their sex is sexist. I hope you agree with that idea. If you do, then swapping the words can simply help put a more unfamiliar form of sexism into clearer view.