So BSAC divers are the best divers in the world and are infallible? Clearly, they have in house BSAC training (no quality control) and are perfectly safe robots who feel no stress in an emergency especially with their superior training.
I don't think BSAC divers are any better or any worse than any other divers, ,why would you believe differently?
From granted, my limited experience, there seems to be little difference in quality control across diver training, with anecdotally, the exception of GUE.
I've done course with quite a few agencies, PADI, BSAC, IANTD, TDI to name a few. Never with GUE, but then, they aren't that keen on CCR, and I have little interest in Cave diving.
In my limited experience, the quality of training is more down to the instructor, than the agency.