This is true. Had the same experience with my DD's. But in the OP's context of Rec Ball and the development of players, what about the other 99%?
Again, this is only my experience, but I didn't ever feel like there was a lack of development happening because of player-pitch at 10U. Although there were good pitchers and not-so-good pitchers, pretty much every girl who was getting regular pitching action on their team was also getting some sort of additional outside instruction (clinic or private instructor). None of the rec team coaches that we came across attempted to instruct pitching mechanics.