Perhaps a bit of incentive from the ground is merited, although I might have focused on helping the rider learn to get the horse quicker off her leg as well, so that when the clinic ends she has some new tools. In all fairness, this isn't a video of the whole lessons, so maybe they did focus on that.
Nice, good-natured horse and a rider who is doing her best, so good for them for putting themselves out there!
The horse does do what HE is asking, but what happens when he goes away??? The reason the horse doesn't move is because the (rider's) aid is mis-timed to the movement of the (inside) hind leg. I have done the same thing as he does (with horses I know) but it is a matter of combining the whip/leg and then withdrawing the whip.
The LY is really more of shoulder in entwicheln, which works well. But does he ever address the need for a spiral seat (shoulders parallel to the horses shoulder, and hips to hips, and looking where the horse looks) as well as location of the legs (inside nearer the girth and outside back).
The horse is slightly sluggish because it is too shortened/low...why sit in this condition of lack of energy? And imho the rider should follow the bascule to allow more energy (in walk/canter)imho.
From what I have heard he (as a dutchman) does believe in lower/rounder as well. And some students have watched him, I have not.