Actually, I think as a broad rule, it's a very reasonable way of organising many sports - at least if women are ever to win anything in those sports.
It would make more sense to just have weight classes in more sports that don't involve fighting, but with criteria besides just weight, and have it be fair that way. You could have like, a midget or something playing in the WNBA and then that'd be fair but not gendered.
Though yeah why do sports need to be organized in a way that allows inferior athletes to win? Isn't the idea of competition to find the best? Isn't the idea of "you're the best...for a woman!" kinda demeaning?
If we've already accepted that women can't beat men in any sports ever before they even try, then I just don't think that's a very interesting competition. It's more interesting to let em all compete together and get the occasional exception to the rule that shows up and competes with the men evenly.
Why should we even care if women win anything in sports ever? If they don't that's their fault isn't it? They're not owed wins, nobody is. People earn em. Most men will never win in any sport ever either. Wanting to have them win to not feel icky about them never winning defeats the point of sports and makes it into a joke.