Notice how Jack's head and body are much farther behind the ball in the muscular swing (left). In the classic swing (right), he's more on top of the ball, with his right leg angled inward. A lateral movement of the left knee and thigh controls the
hips and shoulders, with the left hip moving over the left heel.
Impact
In the muscular swing (left), slightly prior to impact, Jack's chest is facing the ball, one of his key principles. His chin is still tilted to the right, which helps keep his right shoulder back and his right arm close to his body. In the classic swing (right), just past impact, his chest still faces the ball. In both swings, his right heel is more in than up.
Release
In both the muscular and classic swings, Jack's forearms rotate to release the clubhead fully, and his left upper arm stays close to his chest. No chicken wing here. Because the ball is teed, the clubhead is swung upward through impact, resulting from a slightly more tilted spine angle. Note his head is still well back.