Where do you come up with this crap? Anyone who does physical labor with the other sex knows this, especially in the realm of upper body strength. Women can do a pretty good job of making up for it by using lower body strength and mechanical advantage (or simply by being young), but it's a natural fact and no one is disputing it. Sure, there will always be exception, but yeah, men are bigger and have more muscle mass in general.
I know at least 100 people that climb trees for a living. 3 of them are female, and none of those work in the comercial arboriculture where you are expected to work at a high level of production.
As to the rest of the X Y thing I'd say that stereotypes are unfair to the individual, but they are worth considering when looking at large groups of people.