That's not really an indicator of ability. If the boys were trained to throw that way from the start just like the girls were then it's likely there would be way more boy pitchers than girls. Take your best girl softball hitters and put them at the plate at a boys 5A baseball game and see if they fare anywhere near as well as they would in a softball game. Better yet, put your best softball pitcher at the plate and have her sling balls at high school varsity boys and see how many strike outs she can throw. Overhand or underhanded, softball or baseball, take your pick.