I am not going to name names because my point is generic. I am not talking about these individuals to provide a warning; I am talking about the concept that skill in an area does not necessarily equate with teaching ability.
Sure nobody is going to disagree that some of the "best" divers are crappy instructors and potentially even miserable to be around.
But...
This idea has been bugging me for a while regarding this thread as well. I fully agree.
Interestingly enough, when you look at most sports, few of the great coaches were themselves great players. They just have the ability to communicate concepts effectively to people in early stages of their playing careers.
Years ago when I was coaching a high school girls' basketball team I went to a clinic featuring two of the most successful coaches in history, Jody Conrad and Pat Head Summit. They demonstrated a number of concepts using a bunch of local players who had never met them before and who were in fact not even part of a regular team together. It was a revelation. Those two coaches each had a truly remarkable ability to communicate to those players and to us in the audience. In a lifetime of coaching I have never seen anything like it.
I doubt if either one of the coaches could do anything they were teaching at the level they were demanding of the players, but I also bet those players learned more in that one session than any other day in their playing lives.
There is no way I am going to take cave or technical diving instruction from some one who is LESS experienced than myself. Just like I would expect any university faculty I take courses with to be more accomplished in the subject than myself. The greatest teacher in the world following the best teaching and learning theory practices is junk if they have no first hand information to convey and merely reiterate secondary sources.
This is not little league where any old dad can convey the basics of baseball to their 8yos regardless of their own accomplishments in the sport or whether they ever played at all.