In addition to what I say above I wanted to add an unfortunate episode that I heard about in a music school near where I live. The manager was manipulative and rude to the student and the parents, trying to force them into signing up for another year and charging them a bloated price for a cheap guitar that he had rented to the student. I have heard that the teaching approach of this school is authoritative Russian conservatory style.
Per se I have no problem with discipline as I say in the video but I think that teachers sometimes see it as their only recourse and think they are being "good" to the student by forcing them to learn and practice. I think that's rubbish. The only thing that is good for is prison. Or school. Where you need to keep people in line. But it comes at a cost. Enjoyment, and what is the point of playing music if it's not to enjoy?
More than that it corrupts the teacher. Even if he starts off forcing munificently as time goes on and the student (surprise surprise) doesn't enjoy it more and he has to use more force and he ends up believing it is the only way. He begins to think it is a good way to teach (because often these teaches have some success) and he starts to use it on his children, and his clients and so on.
It's just not good.
Use discipline as a tool but use it with love and always try to get the student to apply it rather than the teacher. And remember it is only half the story, without the other half - pleasure - it's not even music.