Paul, believe what you want to believe. But until you examine the fine print on your ticket, you really don't know what you're buying. A very specific example was a plane load of Princess passengers missed a connection in Frankfurt coming home from the cruise. I had a ticket through Lufthansa, the rights on my ticket gave lufthansa the power to assign my ticket to Air Canada on a totally different route to get me home same day. Friends who were travelling home with us bought cruise air. Their cheaper ticket was only good on Lufthansa on that route, it wasn't assignable to an other airline. They had to wait until the next day to fly to Vancouver as Lufthansa only flies once a day.
I as well as Cruise Planner are only trying to point out to people that it's buyer beware and don't fall for all the cruiselines marketing hype of what they will do incase you run into trouble.
If you build in enough leeway and Choiceair is going to save you a lot of money, then sure, i'd book it too. People just need to know what they're buying.