Since it seems like we're never going to agree on if something is empirical or not, let's go back to a more fundamental question:
if you were going to use data to "prove" that panicked divers that are completely out of air don't often go for the reg they know is working (the one in the mouth), what data would you actually need to do that?
If we were going to test that (I might even be inclined to say empirically test it), one would need to take a large enough group of divers, representative of different skill levels, training backgrounds, and geographical locations and force them out of air without their knowledge to observe their behavior. Ok, that test is never going to pass an ethics review board, so I think we're safe to say that test will never happen.
If we were then going to step back and say "well, the test we want to do to actually test our hypothesis isn't feasible", we would be left only looking at reports of incidents that have occurred. To make any sort of claims, we would want that group of reports to be large, representative of different skill levels, training backgrounds, and geographical locations and only look at ones where a panicked diver that believed they were completely out of air and assess their behavior. Someone with a freeflow that allows a "casual" swap to an alternate or has a tank that's running low and swaps preemptively, etc doesn't help. You're trying to determine the "oh ****, I need air NOW" reaction.
The discussion would be much simpler if we actually had the empirical data from the first test. No doubt we could all come up with something in the test procedure that we didn't agree with, but at least there would be something solid to poke at.
If we're limited to just after-the-fact reports of what happened, regardless of if we agree that they're "empirical" or not, for it to even come close to "proving" the hypothesis, we would want to see a sufficiently large group of reports, representative of different skill levels, training backgrounds, and geographical locations made up of only reports of panicked, completely out of air divers. I am not convinced that the bsac reports check even half of those boxes. If you start getting rid of boxes, you're narrowing the applicability of the data. That's fine, as long as that is understood.
That all comes back to my assertion that the data is not empirical and it is not broadly applicable, however, for the narrow application, it may be just fine.
