Thanks for any input! No need for sugarcoating or putting things nicely. He wont be reading this.
I see a lot of good things going on with your sons pitching delivery. As with all young pitchers, I like to work on early momentum and proper weigh shift. But before I discuss weight shift in more detail at another time, one thing I did notice was your sons landing foot. Baseball pitchers must land on a stable front leg (which he does) with the landing knee positioned directly over the middle of the foot in order to gain maximum energy transfer from the lower body to the hips and trunk.
Your son lands across the midline or too open to the glove side which forces his landing knee to be positioned to the outside of the foot rather than over the foot or to the inside of the ankle. This can dramatically reduce velocity and control.
This is more common in young pitchers like your son, because their muscles are not fully capable of supporting as much weight as is needed for explosive pitching. Accuracy is largely about release point and there’s nothing easy about consistent release point if the knee is steering the body left or right as the throw is happening. This is one of the most common factors in a youth pitcher missing left and right in the zone. If the front foot is landing open, the knee will want to follow it. The landing foot being very slightly closed on landing lends itself the best to knee and leg stability.
This is something I would keep an eye on. There are many drills to help correct this movement. As he gets stronger in the lower half, he should be able to correct this on his own, but if he gets used to this movement, it will become harder to correct as he gets older.
Hope this helps