Keep the swing circle intact for a repeatable low point
Keeping the shoulders turning in a circle while the lead (left) arm stays straight and the weight stays forward makes the club bottom out in the same spot every time, which is what produces consistent contact. The coach frames this steady low point as the payoff of maintaining an intact swing 'circle.'
Channel: SagutoGolf
Watch official source at 8:09Why this context matters
Range demo hitting an iron into a launch monitor.