Having dived Aldora many times in the past but only once (a few weeks ago) in recent years, I can explain some of the issues with diving.
1. Having many boats, they do an excellent job of separating divers by ability. In general, the divers in a group are ready to surface at about the same time. (See my next comment for more on this.)
2. There are exceptions. When I dived a few weeks ago, we had a husband and wife pair with us each day. I am sure the husband had plenty of dives, but the wife not so much, and she was low on air long before us. They surfaced by themselves, and we continued the dive. In theory, we were then supposed to surface when the first diver hit 700 PSI, but I don't think that ever happened. None of us wanted to be the one to end the dive, so I think the DM brought us up when he thought we had had enough. Speaking for myself, I was happy to go up every time. We averaged close to 90 minutes per dive, and I would have been plenty pleased with shorter dives. So we all surfaced together, but nobody was complaining.