I don’t think there’s any national or worldwide requirement to follow the CDC in setting out a cruise. These are voluntary choices these lines are using to attract US consumers to come back to cruising.
The biggest issue is there’s still a lot of debate how the disease spread so far on the Diamond Princess, especially the later cases of COVID that appeared. It appears it didn’t come from shared airspace as the cases were so far apart on board, but there were some common denominators in who was serving the cabins (and testing the passengers..)
How does this all roll out? CDC can’t issue guidelines about a threat they’re not sure is using what vector. Cleaning, washing hands, no buffet service? Maybe that might be enough, but the bread and butter of these cruise lines are the most likely to be the most susceptible to risk of death from COVID-19, the over 60 crowd.
We should have some control over our CDC, but can't control other health organizations in other countries or the U.N. WHO. (World Health Organization)
The cruise lines are trying to get a modest startup in our country but our CDC seems to be indifferent.
IMHO if these Cruise Lines can't earn some income in 2020 ;bankruptcies ,(reorganizing) may be in their future next year.
Millions of Americans want to go on a cruise. -Tom