When a student goes to see a teacher they are going to find out what that teacher prefers right away. In Jeff’s case I prefer the right arm to have space, or “carry”, in the first part of the swing, so that when the shaft is parallel to the ground the hands have moved away from the right leg by at least a few inches, if not more. The right arm is not staying tight or straight, however, as this would hyper extend the left arm, but rather is soft and bending a bit until the left arm reaches parallel to the ground. We can see here in Jeff’s swing that he is tucking the right arm in against the body in the takeaway and all through the backswing, and the consequences are apparent in the extremely low (horizontal) position of the left arm at the top of the swing. Jeff’s upper trunk cannot coil as well as it should and when you combine the flat left arm, deep hands, downward hand movement, and slow leg rotation you get a recipe for an in-to-out approach and exit and difficulty keeping the hips in the box.
I think that something as simple as adding right arm width via better upper trunk movement to start the swing and just the thought of separating the upper right arm from the side could make a huge difference in Jeff’s ability to create coil, which would increase his potential to create power and would give his swing more time to unfold, which might make the whole thing feel more fluid and less tight and forced.