Well, I'm going to eat crow here.
I just read
The Quarter Turn That Kills - Cave Diver Harry
And I'm going to admit that the argument made there trumps my logic.
It's not about "making sure we know what we're doing". It's not about "abdicating our responsibility to know our gear."
It's about human error.
The article points out that even the famous Sheck Exley closed his valve all the way, then opened it a quarter turn. BACKWARDS! SHECK EXLEY!
The take away for me was the danger of the quarter turn open, if you make that mistake. Just like the OP of this thread, whether he did it or a crew member did it. If Mr. Exley did it, so might I. Human error. Not the fact that I know my own damned gear. Not the fact that I know which way to turn a screw, for Pete's sake. Human error.
Therefore the logic that trumps my prior reasoning is that the only
foolproof test of a valve is one which looks at only two conditions: either all the way open, or all the way closed. If that's what you were trying to tell me,
@JohnnyC , I missed it. If a diver has one state or the other, and
nothing in between, he'll be able to tell before he splashes.
I'm going to change the way I teach.