When the body remains in control
of the tempo, the arms will not initiate
the downswing, and why should they?
The handle cracks the whip, not the other
way around. If you watch the slow motion
Nike Tiger Woods video, it's plain from that
full position at the top he gets to on the
big swing that his hands just naturally follow
the same path they took to get him there,
only in the reverse direction.
That is, the first move Tiger's hands make
on the way down are (basically) to the rear.
They are following the arc of the swing
back down into the hitting zone.