My son’s pitching coach taped him today and we looked at it in as slow motion as his system would allow. My son looks like he throws 3/4 at best, but when looking at the film, right before his foot plants and his arm starts froward he has very much the look of a kid that would throw more over hand. Somewhere between then and the point of release the arm drops down. His coach wondered that maybe he’s developing so much torque that his muscles can’t handle it causing his arm to fall. He said he sees no major flaws, he opens up a little with his hips and shoulders, but nothing to be concerned about, but he did act somewhat befuddled as to why he would look so good right before planting but then release at the slot he does.
He’s 10 and at 80% hitting 52-55 mph, grunting at 60.
Assuming the pitching coach is a good one, it doesn’t sound like you have anything really to worry about here. Based on your son’s early age (10), it could be that your son needs a few years for him to develop more arm strength in his arm to control his throws. Over time, you may see him go to more of an overhand throw; however, if he remains at 3/4ths, this should not be a problem either.