I think it's more a case of all the people whose cruise has or is about to be cancelled have taken a voucher instead of the cash refund and those vouchers need to be used up by end of 2021. On the other hand a look at cruise critic posters suggests that if it didn't happen in the US then it didn't happen at all.
I was posting to a comment there when an american was saying they hoped the Australian NZ cruise would proceed in September.
I posted that it was possible that international travel for Australians was likely to be stopped until end of year according to yesterday's headlines, let alone letting non Aus citizens into the country and then to go on a cruise. They pretty much didn't believe me and needed me to send the links. I surmised that It also suggests that google doesn't work for people from the US.