The big thing is he's making a big assumption that there's some natural limit to the total infection rate that can be achieved by the virus - less than 100% and

The big thing is he's making a big assumption that there's some natural limit to the total infection rate that can be achieved by the virus - less than 100% and less than the 30% of the cruise ship. That seems plausible but it's essentially based on zero evidence. Diseases have wiped out societies so there's no rule I can saying Covid couldn't achieve a disastrous 30% penetration of the population. No country has had the guts just say "let's see how far this can go" and fortunately so. An extreme worst case would be maybe 3% of the population dying. The Syrian civil war killed 2% of the Syrian population over several years, so this sounds bad. But US regular death rate is about 0.88% you could fudge and claim people would barely notice. But Covids is a very messy death and would destroy the health care system, which people would notice.