There are several teaching/certifying organizations, and they aren’t always "on the same page" about what to teach.
Long ago I got halfway through an instructor training school that had the philosophy that they would make me into a great diver, and then I would make my own teaching program to teach! No support from headquarters! That is why PADI got so big, they give their instructors a well laid out system of teaching that covers what the beginner needs to know. (No, not an advertisement for this agency, just my experience)