Can you do me a favor ... review the link you provided and talk us through the usage of the hands during the first of the two drills that was about the hands. Exactly how is he using his hands during that first drill?
Sorry for late response. I was pretty tired last night.
Brauns drill is pretty basic but very helpful. It gives the proper feel of load and release of the hands. An isolation drill. During this drill I would inform the player of soft wrists and hammering with the top hand.
The drill imo is great for teaching the path ‘down to’ the ball. As well as release points(so important)above the ball.
Setting up the tee high/outside provides the player with a sense of direction as well as load and release of hands/barrel above the ball. I use this drill as a warm up for my lessons. I will progress to the drill Eric Hosmer does with the bat between his legs with front toss. Eventually moving towards full speed front toss.
If your asking for anatomical descriptions. I’m not the guy to be describing such intricate details. Hopefully this helps everyone understand what the drill(s) are about. Swinging with hands/knob has gotten a bad reputation for along time. Hand path/barrel path is right up there as fundamentals that make all the difference. Balance and load would be the others.IMO