He's Right Arm Swinging. The Hinge Pin is his Right Elbow.
He Cocks his Right Wrist. It looks like a Snap Release. Technically, it's not a Snap Release because his Right Wrist begins to Uncock during his Downstroke.
He has no need for a Left Arm except to Pull his Right Elbow as far Forward as possible. His Tilt and Left arm serve to get his Right Elbow to the Ball.
Note that if he were a Left Arm Swinger, he would be playing his Ball Forward of Low Point.
So Bently J. Doyle is teaching right arm swinging now??? Wow.