Firstly, the head does move in most hitters during the loading process-some as much as 1-2 feet. The key is that it doesn’t move much once the hitter is in a true loaded or launch position. Only forward and down IF fooled by pitch and are adjusting to an off speed pitch.
Next, The head moves from up to down like watching a pitch on TV from top of screen to bottom and the upper body rotates around the center(head) where the the head appears to end on or near back shoulder.
And lastly, we as humans, do not possess the capability to follow a pitch into catchers glove-we lose sight of it in front of plate.