PS: It might have been the same DM that I once saw send his computer up attached to his SMB before the end of a dive.
...and I saw a DM send his computer down on a line at the end of a dive so it could do the required deco. At least in that case it was a little more reasonable, because he had done the dive on nitrox, but the computer was on air.
None of that surprises me. I remember a DM that would use one computer for morning dives and another for afternoon dives.
Of course I've heard stories from older cave divers, like tying a line to their computer before moving to the next stop so the computer doesn't lock up from skipping parts of deco.