I don't agree with either of these. Relying on that elastic stretch reflex to throw the hook is a recipe for shoulder injury. There's a bit of drag on the hook to get it going sometimes, but you should never whip the hook into the target to the point where your shoulder is well ahead of your fist.
As for Bas, he doesn't know as much about scientific striking as he thinks he does. Don't get me wrong, he knows a lot of good shit, but I wouldn't go to a Kyokushin guy first if I wanted to learn about left hooks.
To put his advice in perspective: Bas also used to say that the jab is useless in MMA.
I agree with this, this is stretch reflex used in the wrong way, and learning to throw hook with exaggerated "elbow/fist behind shoulder" is both technically wrong and dangerous IMO. I was initially taught this way and my shoulder wasn't too happy, especially if the punch connects while your elbow is still behind the shoulder. To use stretch reflex to a degree, to build momentum is ok, but to rely completely on it is dangerous, not to mention that the punch is telegraphed and slow.