I watched that video over 10 times at full screen size and stopped it at various points, and my conclusion is that he looks continuously at the target ball as he is moving his body down into his stance. Once he is set in his stance then he looks back and forth between the cue ball and target ball, as he did when he was standing.
Myself I have found my point of aim on the object ball and the line I want the cue ball to follow while standing square to the shot. As I stride into the shot, I am focused on that line and putting my cue stick on the line. I maintain more of wide angle view that confirms my alignment. As I am bending down to set the bridge I shift from the long range to the short range, to be sure of my bridge placement and the tip's distance from the cue ball. While doing this I maintaining a wide angle view. So the bending over is a transition from long range to short range with a lack of sharp focus on any one thing. As the bridge is set I focus on the cue ball and start the back and forth to object ball.