My theory is that one reason why retention rates are so incredibly pure is partially due to the fact that most mainstream training is so poor with subjective standards instead of objective requirements, as well as so many students being placed on their knees and having zero buoyancy control after open water. When people start out diving and they are not skilled, they know it subconsciously. I say this on the statistically insignificant observations of my own retention rates when I started teaching (on the knees) versus today (never on the knees). No one corks/craters today. Pretty much everyone did when I started out. Instructors who teach on the knees who say that their students don't cork/crater are lying. I've dove with some of their students and they did exactly that every time.
Everything you mention here is a matter of how an individual instructor teaches their course, has nothing to do with any particular agency or the general state of scuba instruction in the industry. I'm sure everyone generally agrees that the quality of instruction for any scuba course is dependent on the quality of the instructor, regardless of their agency affiliation.
So if you are saying that some instructors are more effective than others, I don't think you'll get much argument.