Not knowing anything about this incident other than what I read here, I have a comment some people might find interesting. I actually experienced something like this on that very wreck about 6-7 years ago, and it might be instructive.
One thing we don't know is the starting point for the length of time mentioned, and we don't know how the divers were planning to ascend. In my case, the dive operation had attached a line to the wreck, but that operation no longer exists, and it is more likely that divers were ascending under DSMBs. In my case, all divers ascended on the same line leading to a float. Before the dive, the DM went to each group to get their dive plans so they would know when people were doing their final deco stops and reaching the surface.
Everyone had nearly the same dive plan, and the only two rebreather divers on the boat, sitting next to us, had exactly the same plan as our group--same GFs and same run time. Our two groups had the longest planned times on the boat, and, as expected, we were the last ones to the ascent line, with us getting there just before them. Our group ascended at 30 FPM, and after awhile, I looked down and could not see any sign of the rebreather divers below me. I was a little worried. Had something gone wrong? When we reached our first stop, I looked down continually, hoping to see them. Nothing, including, of course, no bubbles.
It was not until we were on about our 3rd stop that I picked them out of the gloom far below me. When we were doing our final, long stop, I could see them several stops below us. All the other divers were out of the water. When we got out of the water, almost exactly at our planned time, the DM came to us, clearly worried. We assured them that the rebreather divers were on the line, but something must have happened during the ascent, because they would not be up for a while.
When they finally got back on the boat, the DM asked them what had happened to their dive plan, and they said they didn't know. Everything was right on schedule when they started the ascent, but their computers kept adding time as they ascended. I commented that they had ascended very slowly, and one of them looked at me like I was an idiot. "You're supposed to ascend slowly!" he said.
What had obviously happened is that by ascending as slowly as they did, they had essentially added more bottom time to their dive, and their computers had responded by adding more deco time. They ended up doing about 15 more minutes than planned, much to the concern of the boat crew.
By coincidence, a few months later I met the author of a major agency's technical rebreather course, and she flat out said that ascending too slowly--often far too slowly--was the most common problem with rebreather divers. Because they are not gas limited, they tend to ascend at exaggeratedly slow rates, and their computers adjust by adding deco time. She told about a recent time where she had ascended at the standard 30 FPM and had had to pass all the other rebreather divers inching their way up the ascent line. Back on the boat, they had admonished her about her 'rocket-like" ascent rate.
