what's notable that no one seems to recognize is that here is a big difference in 'sheltering' in your concrete
apartment, with the windows open, being able to go out in the common area and walk for a little while each day.
and sheltering in your cabin on a cruise ship where the majority of customers can only get by with CIRCULATED air and an hour on deck.
The air in a cruise ship relies on multiple individual HVAC systems thruought the ship. Each gathers air from all those cabins, sucked thru the circulation box, mixes with a little fresh air, and pumps it back into those rooms. If someone is sick in one area covered by that HVAC system, air from their cabins is being pumped into those that aren't sick. And since the HVAC ductwork is metal, and the air is reasonably cool, the virus can survive.
I'll bet at some point there will be a study about exactly that, and how the HVAC systems both protected a large amount of passengers, and contributed to 700 people finally being exposed.I think they will also find that passengers who had cabins with porches and windows to open will have fared better.