I agree that the context needs to be brought into proper perspective. The learning and teaching styles for both instructor and student need to be in sync. For this I'd recommend (in addition to recommendations of others) perhaps calling the instructor directly and getting to know them a bit before signing up. I think that for basic OW skills and certs, an open dialogue with encouragement and relatively positive feedback is a good thing.
I do believe, however, that the game changes completely when it comes to the advanced Technical certifications(Cave, AN, DT, Rebreather), as is the case in the OPs example. Quite frankly not everyone should be doing it especially if they don't have the skillset; I don't care how much money you throw at them. It puts the instructors and those who dive with that student in the future in a precarious situation.
When a person "holds themselves out as" and presents C-cards showing AOW, or Master Diver, or 1000 dives diver, etc. I believe that it should be safe to assume that a solid (not just basic) level of understanding and skillset (buoyancy, finning, gas management, no-reference ascent descent and stops, and self awareness/control) has been reached, or they shouldn't be pursuing said advanced certification yet. The advanced certification instructor is there to teach just that; not to waste time going over remedial techniques that should have already been mastered. In fact, I'd be pissed if I had paid good money to "learn from the best" and a fellow student was wasting everyone's time over something "basic". It is also very possible, that in those advanced classes (cave in particular) that if a student "doesn't get something but is still trying very hard" it will still 100% put them or someone else in a dangerous or deadly situation. It's not either-or. Trying does not remove the element of danger, nor does trying entitle a pass to the cert if the instructor doesn't feel the student is ready.
Reminds me of the time in my office that one of my employees was boasting about how he just got his firearm concealed carry license and wanted to pursue his instructor certification and to begin competitive match shooting because he had just obtained his pistol sharpshooter rating at his local range over the weekend. He thought he was "badass" because he was "ahead of the curve" and none of his friends had got their CC or sharpshooter yet. Out of curiosity, I asked if he was carrying (no problem if he was). He said "Yes, here I just got a new holster, let me show you...", and proceeded to show me his very nice Kimber Ultracarry2, unholster it, and set it on my desk (without checking the chamber or removing the magazine) and POINTING THE BARREL DIRECTLY AT ME. I looked up at him with a very surprised look and said "I'd appreciate it if you pointed that away from me".
His response: "Huh? Oh yeah, I just forgot, it's no big deal the safety is on". Guess what? I yelled at him. My whole office (and probably the suites next door) heard me yell at him and watched me throw him out of my office along with some very colorful commentary about how he had no business pursuing certs as an instructor with that attitude. Have the basics down first.