Thank you for posting this. This is what I had been thinking all along, just as "common" knowledge but I hadn't looked up anything. That's why I felt surprised at so many early reports saying all passengers should have been on deck.
Speaking generally, I think the thought is that a boat is not going to sink. If going on that assumption, it seems dangerous to have passengers on deck during a tumultuous storm as there is a liklihood they could be swept overboard, as well as they could get injured or be in the way of working crew during that time. Also, even if a ship takes on some water, it's ok. There are usually hatches to shut to localize the issue, etc. Obviously, in some cases, there are times when everyone is brought on deck because the decision has been made to abandon ship.
If there was a downdraft as has been suggested, I think the impact was catastrophic very quickly. And there may not have been an official decision/process to abandon ship because events transpired quickly/survivors may have been washed overboard. If the electrical systems had already failed, how would they have made an announcement to the lower berths?
Just musing and MOO only.