This is a good question, especially for non-North American cruise itineraries.
My wife and I are on B13B starting January 2, 2023 in Sydney, AUS. I know it can be "fun" to check-in on-line for an upcoming vacation,...but not 13 times! That said, even if such check-in isn't technically required, given the vaccine and negative Covid-19 RAT requirements in the Oceania area of the world, this is something I think we'll look into more closely and report back on here. Really not wanting to take 26 RAT tests with us to Australia, for example!
If anyone has done B2B in Australia, NZ, Fiji etc recently, let me know how the Covid-19 testing issue has been handled.