Pure pseudoscience observation, but I feel like with the women there's a critical mass missing to being able to generate rotational power and actually getting the trunk into punishes rather than just the arms. Even the wmma girls that look like they know what they're doing don't have that actual stunning power.
Nunes hits like a man with training. The broadness is what's stuck out to me as different with her. Maybe once into athletic men's size, that critical line is crossed so anything more doesn't much matter? (cause you're dead on about those guys being built and they can maul people, but don't have sleeping power) Maybe it is just like the movie Goon, some people are simply touched by the fist of God, and that's all there is to who does and doesn't have that one punch knockout power.
Also, KO power is the only, only thing Jones doesn't have.