Actually, since men usually have broad sholders and other diffrences in their skeletal structure (I emphasise usually), they have naturally better mechanics for throwing things. Pitchers have things called "Rotator Cuff Exercises" where you do a repetitive motion using little or no weight (I bet all you high-schoolers know that excerise.) to increase your arm speed. The muscle mass of your arm is actually a minor detail. Of course, this merely means that women have to use diffrent mechanics than men do.

It's possible that merely no one has gone to the trouble of figuring out how women can routinely throw 110mph fastballs, because the mechanics would/should be completely diffrent due to the afforementioned skeletal diffrences. I think 'throws like a girl' is an apt description for a man who cannot throw well, espically if he throws with form similar to that of how a girl would naturally think to throw (instinctively, because of, well, skeletal structure!).