I think there is a lot of truth in this. How attractive you are to women is not necessarily how threatening you are to other men, but it is how threatening you are CAPABLE of being to other men.
If someone pointed a gun at you about to shoot you, would you have any qualms about defending yourself?
If you were in a boxing ring with all of the world's men, would you stay and fight, or would you run for the nearest exit?
I think being able to fight and being prepared to fight (but choosing not to unless it's really necessary) is huge. A large part of that is mental. But when two men are both mentally matched, it comes down to the physical.
This is why women often like big, tall muscular guys automatically before even getting to know them- they look threatening to other guys.