Looks much improved since the earlier videos - better coordination and strength. Better mechanics too.
I do think he’s not fully using his lower half but that’s fairly common for young kids. You could have him start practicing the NPA’s Hershiser drill and Cross-over drill to start getting him to use to shifting his center of mass (i.e. his hips or butt).
It also looks like his “equal & opposite” is off a little in that his glove arm is a little short compared to his throwing arm. A short front side is a quick front side which can lead to early shoulder rotation. Get his to extend his glove arm more to match his throwing arm.
Finally, keep an eye on the head tilt. It’s best to keep the head upright.