"1) Rebooking customers at no cost after a significant schedule change is an obligation according to most airline T&Cs and many regulatory agencies. The cruise line didn't do a special favor or exhibit particularly good customer service here."
There is a tremendous difference between the way an airline does it and the way Seabourn does it. A while back whatever airline Seabourn had booked for me changed their schedule so that it showed an impossible connection from Stockholm to Las Vegas. I made the mistake of calling the airline and settling for a not very good correction. Then I was sorry I hadn't held out for something better and called Seabourn and was told that since I had contacted the airline directly, it was now out of their hands. Had I called Seabourn directly, they would have been able to offer me choices including all the airlines they work with.