Shallowing the swing is a frequent recommendation.
–For the drive it reduces the “angle of attack” reducing backspin and thereby optimizing distance.
–For the irons it enables the trajectory and backspin to be more uniform.
Most importantly it is a major factor in improving our shot dispersion allowing us to play to narrower fairways and tighter pins.

The towel drill used in the video demonstrates a maintained relationship between the right arm and the torso. The right arm does not need to be touching the torso, it just needs to move circularly with the torso and not up and away from it.

In the demonstration, you may note that my left arm is far from being straight. A shoulder injury from many years ago has restricted by arm rotation.