This is Pivot Lag (with its Downstroke Shoulder Turn Lag per 6-B-4-C) and the Downstroke Release Sequence as explained in 2-M-1.
For those who believe that the 'Magic of the Right Forearm' involves a straightening of the Right Elbow ('Forearm' action) from the Top, please understand that there may be a tremendous difference between Feel and Real.
The Pivot Delivers the Power Package -- Assembled, Loaded and intact with its Power Stored -- deep into the Downstroke. Only then is it Released (the lengthening of the Third Side of the Triangle, the straightening Right Arm).