Demonstration and ability
this on facebook. There was a question about the up and down in his form. The explanation is that he was demonstrating to a specific group of students.
For the sake of certain student group and certain audience, the demonstrator usually slows down or speeds up. He may also change rhythm so that the audience can "see" more. To claim that because the audience is at a lower level, the demonstrator will willingly perform wrong moves is a simple excuse for a poor demonstration.