H - Are you referring to the guy with the paint sticks (my link), or another video from one of your links? Actually the paint stick model shown doesn't give the whole effect of the double pendulum, because it only has one pivot point. What I was trying to point out was how this particular model demonstrates the wrists being released by the forces of the semi-circular hand path (centrifugal force). I agree that completely straitening the front arm elbow joint is a "compromised" position - and a weak one at that. On that note, when I hear sports announcers say "they really got extended", I cringe thinking kids will pick up on that thinking they should fully extend their arms at contact. NOT what great hitters do! -unless fooled on an outside pitch.
Now those links you posted are gonna keep me occupied for some time...