But the head influences his extension (pic 3-4) and his spine angle. Kyle is beginning this, so it make sense to avoid unnecessary moves that can harm his game. Fleetwood is a great pro and able to do his swing successful.
My thought is if his head rotates back "a little", not a lot, say an inch or two, but he keeps it there through impact (not keep rotating back....then not rotate back to center on the downswing), then it wouldn't be a problem. I think you're pointing out that his head is moving in concert with his shoulders which I certainly agree creates unnecessary movement.
But the head influences his extension (pic 3-4) and his spine angle. Kyle is beginning this, so it make sense to avoid unnecessary moves that can harm his game. Fleetwood is a great pro and able to do his swing successful.