Over the years I have met many instructors who are mistaken about many standards. I have been wrong on a number of occasions myself, chiefly in my earliest years of instruction. What happens is you work for a few years (as I did ) as a DM and then an AI assisting classes. You learn to do what the instructors you are assisting do, and you assume they are right about everything.But a PADI instructor I assisted in 2012 said she didn't allow drown-proofing.
I would say the best example of this is the reaction we got when we published the article on teaching OW classes with students neutrally buoyant and horizontal rather than kneeling on the bottom of the pool. We had very, very rencorous threads on ScubaBoard featuring instructors fairly screaming in print that standards demanded that students must kneel on the bottom of the pool to learn skills. When I published a direct quote from PADI headquarters saying there was no such standard and it was perfectly acceptable to teach students while neutrally buoyant from the very beginning of the class, one instructor replied that when you get a statement from PADI headquarters explaining PADI policy, it is just the opinion of the guy who answered you, and he could be wrong. If you actually did what that representative from PADI headquarters said you could do, PADI would expel you.
I would guess that now, 7 years later, a sizeable portion of the world's instructors, possibly the majority, still believe that teaching students while they kneel on the bottom is a standard.