There are a lot of fuzzy lines between what's fantastic and what's merely genre convention.
For example, there are all sorts of books and movies in which someone can be bonked on the head to render them unconscious--for more than a few seconds, mind--without any serious after-effects. This is wildly unrealistic, but we generally don't call it a mark of "fantasy"; it's just genre convention.
Action movies where a car is shot, and then suddenly explodes into a billowing column of glorious flame? We don't call it fantasy. Romance movies where stalking someone brings you true love instead of a restraining order? Not called fantasy. Historical movies with major factual errors? It's not called fantasy.
So the initial post--which frankly comes across as trolling, but I'll take it as if it's serious--wherein "normal sized women who can trade all-out punches with large male professional fighters, not get badly hurt, and win" barely even pings the meter for what's accepted as a story that's not labeled fantasy. That's far, far lower on the scale of breaks from reality than "We'll just bop the guard over the head to get past him, and that's safe! It's not like we've just caused permanent long-term brain damage to an innocent man, just because he's still shown to be unconscious from head trauma several minutes later!"