I was folding some large sheets of endpapering this morning, and thought of my first bookbinding course. It was a home study thing, so I was watching a video and didn't have any direct input from the teacher, but I was sure if I followed the instructions exactly it would all work out in the end.
After running us through the whole saga of paper grain, we got down to actual work and she showed us how to fold a piece of paper. She said that if you started the fold at either edge of the paper you would get little creases in the middle, and dictated that you must always press the fold down starting from the middle and pressing towards each side. She said that several times, just to make sure we got it.
Until then I had been pressing from the side and had no little creases. Under her instruction I started pressing from the centre and soon had lots of trouble with creases. But I was paying for the class, the teacher was well-known and respected, and I wanted to do what the teacher said. I persevered, and eventually developed a technique for starting at the centre and folding towards each side and not getting any creases most of the time. But it wasn't easy.
Flash forward a year until I started working at the bindery. The very first day I was told to fold some large sheets of paper. Aha! Something I know how to do! I confidently folded the paper the way I'd been instructed.
Wrong! The bindery manager had apprenticed in London and worked in a variety of binderies for many years before moving to Canada. He knew his folding. Mine was wrong, wrong, wrong. How should I have done it? Exactly the way I had been doing it right at the beginning before I had any instruction, of course. The way that I did it where I had no trouble at all with little creases.
So was the teacher wrong, wrong, wrong? No, I don't think so. The teacher was telling us the way she did it, and outlining the problems she had had that she had solved her way - which is pretty well the only way anybody can teach. It is up to the student to receive the teaching, practice what they're taught, and when they've reached a level of confidence they can then decide whether they want to follow what they were told, or do something else.