Time is of the Essence
 

A right-handed archer holds the bow in in left hand. He does not swap hands or drop the bow to reload. The English longbowmen carried approximately 72 arrows each in a battle, which they could fire off in minutes at their maximum rate of fire. Speed was essential so they would not be swapping hands during a battle to pull another arrow. They would have pulled the arrow with their right hand whether the arrows were in a quiver or not.

If I'm not mistaken, I don't think he meant that literally, as in an actual archer in the act of drawing and firing an arrow. He was just referring to the fact that, according to TGM, the "arrow from the quiver" motion can be performed with either the left or the right hand, while only the right hand is ever capable of driving (for a right handed golfer).

Its not left arm power but moved by a force placed apon it created by the pivot.
The left arm is always swinging. The arrow from the quiver is just an analogy for the longitudinal acceleration of the secondary lever assembly.