What I like about the video James posted is the knob will replace the front elbow. The front elbow will change levels depending on where the pitch is located. IMO get's things moving the right direction. Of course the front elbow needs to be working properly, .I'm more of a knob (immediately) up guy as the cue and then teaching how proper tilt takes the barrel to all positions high to low. That's what I see Miggy doing in the multiple swing GIF that often floats around.
That said, the video above is not bad, and shows a lot of the paths to avoid as far as around-the-ball, casting, etc. The issue in my mind is that the knob knock the ball off the tee demo he shows works for a relatively high location as is shown. The problem is if it trains you to also start pushing the knob *forward* like that (rather than more immediately UP) on a lower pitch locations, which I think that kind of knob-forward instruction can often lead to.
I think you need to be careful when using the word "up". It's way too literal for a young hitter, for example "how far up?"
In the Trout swing below.. is the knob immediately going "up"? I don't think so.. I believe the knob replacing the front elbow is more applicable in this swing
Same thing here as well, I'm not seeing the knob going up immediately