Agreed, it needs to be fixed sooner rather than later. But lets look at another angle. You have 17 other 10u players (8 on the field and 9 on the other team) that need to get playing (development) time and if the umps are calling a leap on every other pitch, they're being robbed of their opportunity. Because it will be called on almost every pitch at the 10u level if a girl is doing it. That habit is not getting fixed during a game, it will be fixed in the backyard.And here is where the problem begins. Prime example of letting it go at the younger ages because they are just learning and are so young. Parents and coaches then have no reason to try to get the player to break the habit because, “They never call it anyway.” Player then continues to pitch this way and all of a sudden when she’s older and it is getting called in HS, she falls apart. Why not use it as a teaching moment at this age so that they are forced to correct it before the muscle memory becomes too difficult to fix? I get that this may sound harsh at 10U but the umpires are not doing this player a favor at that age by allowing it to continue.
So I actually fall on the side of the umpire here. Point it out after the game to the coach and kid. Use it as a teaching moment but don't make the other players have to sit through a terrible game.