That video's all German to me, but that demonstration is pretty clear ... when it's hitting the fan, would sure suck to not have your QR work.
Another one of those safety systems you learn and forget about.....if your harness has a hook knife, do you know where it is? Can you reach it blind? Before heading out into a little hairier situation than I'm used to, my buddy ran through the safety systems including hook knife ... and hate to admit, I couldn't find it (it's placement is quite awkward to reach even when you know where it is). For this to be a good safety, I figure you have to be familiar enough with it to be able to pull it while being dragged underwater at 20mph.
So for a really great simulation, you can get dragged behind a boat tied on with line, to see if you can cut yourself loose.