Here is how it works Kinesiologically.
The ball can not make forwards math until the Humerus is fully outwardly rotated.
This is the point when lengthening ends and shortening starts. lengthening ends long after leg lift and drop in where the body comes to a complete stop eliminating all previous forwards momentum
(no forwards math there) at that point.
Because our bodies work off the walking response, the glove side leg has to establish ground stabilization to even start the shortening process signaling and only after the Humerus is fully outwardly rotated. When using the traditional Humeral/Forearm transitional timing to length, your Humerus is much later in achieving outwards rotation to length, meaning any forwardness before that is wasted into the ground as heat, it is why you see ground piled up towards home plate instead of second base where it should be like coach Newton teaches us.
In the future when everybody finally understands this you will see the pitchers facing the batters with their feet directed forwards the way we are built to motor forwards. Pitchers will stride shorter, stay taller all the way through the delivery and recovery by rotating fully 180 degrees.
It has already started but because info is delivered from the top down (I must see a MLB pitcher do it first) it will remain secretive and slow to recognize by the bottom uppers.
Go ahead and start from the stretch, there is no advantage in all the leg lift motions that are taught now. Have him turn his ball side foot towards home plate
Hopefully High school and College rules regulators will go back to original baseball rules instead of their useless efforts in the last few years that limits foot positions that cause Knee and hip injury!