Consider this, the tests appeared to be faulty or at the least flawed, returning false positives, as was eventually discovered, BUT under the Current CSO if they were to sail on the test cruise and they got postive tests returned during or at the end of the cruise, the CDC would "fail" DCL on the simulation cruise and they would lower their status. By cancelling they can potentially regain a green status after long enough quarantine, which very probably by then the CDC's Conditional Sail Order will change from Manatory conditions to "Recommended" ones, and opens the door to potentially getting them to resume cruising under the recommended 95/98% Guest/Crew vaccination requirements. And possibly following RCCL's policy of requesting voluntary proof of vaccination, and those that aren't vaccinated (with the exception of children under 12) would be subject to stricter protocols and possible bear the cost for testing on boarding, mid cruise and before embarkation at the end of the cruise. That hopefully encourages those unvaccinated to get the shot as it would economically would benefit them. Although Disney sails with a significant number of children, many under 12, hopefully they would be able to conduct reduced capacity sailings under the CDC's recommended vaccinated guidelines. We shall see.