We've heard - over and over - that there is usually more than one way to do many things.
And I agree.
But why get upset if an instructor only demonstrates one way of accomplishing something?
Most classes have time constraints on them.
Sometimes it's a challenge to just get one idea across - forget about variations on a theme.
I would think it would be easier to try to keep a group "on track" if most of the members are doing the same thing more-or-less the same way at the same time.
I read over and over about "poor teachers/instructors" - but the student/learner/tutee has to do his/her part, also, to make a class successful or a learning experience positive.
(I'm not an instructor - but I have had some obnoxious/disruptive/unprepared classmates now and then)