The hips turn less than the chest on the backswing, the chest less then the left shoulder complex, the left shoulder less than the hands, the hands less than the club.
Early in the downswing, the hips lead the chest, which lead the left shoulder, arms, hands, and clubhead.
If they all continued through impact at the same rate, you'd have a great big mess.
Why?
Because there would be no way to put the clubhead speed needed into the club. (plus a whole bunch of club delivery issues)
Remember, the clubhead is going relatively slow when the whole train is moving together!
Is centrifugal force involved here with the center being the pivot which slows down? The part I don't understand is how does the pivot slow down at the proper time?