For me, its extremely difficult telling a whole lot with the picture changing from pitch to pitch, and from that particular perspective. It looks like the camera was somewhere between home and 3rd. Get some video from as close to directly behind the plate and at belt level as possible. What would be perfect is a camera mounted at tee height and the middle of the plate behind a piece of plexi-glass, with a narrative of what pitch was being thrown and what location was attempting to be hit.
But using what’s available, it looks to me like his biggest problem is extremely inconsistent mechanics, but its difficult to say without knowing why he was in the stretch for every pitch, what pitches he was attempting to execute, and where he was trying to locate the pitch.
There are about a million drills that are used to correct inconsistent mechanics, but you have to work on very specific things, not try to fix too many things at the same time, and definitely not be in any kind of a rush. Faster usually works out to be slower.
I’m gonna take a wild guess and say he was never taught to play with proper basic fundies, and even now allows his fundies to get sloppy when he plays catch. Proper basic fundies to me are, step directly at the target, get the hand back into a good setup position, focus on the target, and follow through, all while maintaining balance.
You’d be surprised at how much his pitching will improve once he knows how to play catch correctly.
But don’t get too caught up in anything right now. At his age, just make sure he’s having fun and doesn’t get hurt.