@JackD342, It sounds as if you are saying a diver in an emergency only needs a spare air source need by. If that is the case, can we dispense with all the skills evaluation in solo/self-reliant classes and just strap an extra tank on people?
Now, it may well be that a DM/Instructor has those skills, from experience. But that only seems assured if you make DM/Instructor come after self-reliant/solo.
It seems difficult to argue that the students need to learn to be effective buddies, while saying the instructor needs no effective buddy, just an air source, without being explicit about why. Such as the skills, and possibly gear, those classes promote.
I teach no solo/self-reliant classes and given the cost and time to be a DM/Instructor I do not thing they add significant hurdles for the diver or profit for the dive shop. ETA: they might slow the zero-to-hero path though.
ETA: I'm not arguing the DM should be the instructor's buddy. I'm arguing both need to be self-reliant, as they may be with other than their own top-flight students. And that sometimes they are actually alone in the water, which sends a bit of a mixed message. Unless they say: 'after X dives, I got training in Y, and have Z redundant gear, as can you later if you have the aptitude for it.'