In my experience, cruise line tourists are not very healthy. They certainly are older. The workers are much younger of course, so you have about a third of the ship in their 20s. I presume they were included in the sampling. I like your estimate, but would broaden it to 1% to 4%, I'm not sure the tenth of a percent is a significant figure. My guess is for western countries without unusual comorbidities. Belgium apparently counts differently, so their situation may not be so dire.
There is some chance the disease is much more widely spread of course, say a factor of 5x to even 20x. There is some chance we are undercounting fatalities by 2x.