When a person walks and their hands are being held behind their back the shoulder movement is exagerated due to several factors. The body is having to compensate for this abnormal arm position for balancing purposes as each leg and foot move forward, 2. With the arms and hands held behind the body they will naturally rest on top of the upper backside of the hips and buttocks. This will also exagerate the movement of the shoulders as one walks. Also noteworthy, there are "people" standing outside of this garage witnessing this, no matter who they are, likely Mil, notice how high and straight she is holding her head as if to say, "this is outrageous, I am the SOTH".
Nancy Pelosi is in handcuffs in this video.