Yes, the right shoulder is part of the pivot, but since it is braced in the Hit, it isn't spun. If it were, #4 would be one of the Hitting Accumulators, but it is not.
The Right Shoulder does "Backstop" the Thrust from the #1 Accumulator but that does not mean that the Right Shoulder stops moving. Additionally, the Right Shoulder can produce significant Speed and backed by the Power of the Pivot.
Zero out the Pivot and Zero out the mechanical advantage of accumulator #1 by holding the Clubhead in your right hand. How far can you hit the ball?
Quote:
6-B-1-0 THE FIRST POWER ACCUMULATOR is the Bent Right Arm – the Hitter’s (7-19) Muscle Power Accumulator. Even though the Right Bicep is active per 7-3, the Backstroke (8-5) is always made with the Right Arm striving to remain straight. But the straight Left Arm restrains this continuous Extensor Action of the right triceps with and effortless Checkrein Action. Consequently, during Release (7-24) the Right Arm can straighten only as the Left Arm moves away from the Right Shoulder. This results in a smooth, even Thrust for acceleration of the Lever Assemblies (6-A) from an otherwise unruly force. Active or Passive, the straightening Right Elbow with its Paddle wheel Action, powers, guides, and regulates the #3 Accumulator Motion (7-1 but not the actual Clubface aligning (1-F). Study 2-M, 7-11 and Components 19.
6-B-1-A MAXIMUM POWER is produced by adjusting the Hand speed to permit maximum Thrust through Impact before maximum extension is reached.
6-B-1-B ZERO ACCUMULATION is possible only when Accumulator #4 alone actuates the Primary Lever Assembly.
6-B-1-C MAXIMUM TRIGGER DELAY is gained by causing the Right Elbow to “Pass the Ball’ – which is the Line-of-Sight-to-the-Ball- before Release. Study 2-N, 3-F-7, 7-8 and 10-14.
Read 6-B-1-B, 10 times. So, there are degrees of use.
Homer seems to be saying that the #1 Accumulator does not move the Left Arm. He says that the Right Arm can Only Straighten when the Left Arm Moves away from the Right Shoulder.
Lastly, note that "Paddle-Wheel" Action, is mainly an attribute of the Right Elbow.
Notes for further discussion: Extensor Action is a Below Plane force. It does not move the Primary Lever.