I don't see any disagreement here....
Anyone can get the price change or upgrade IF you are still in the period before final payment is due (usually about 90 days out for a 7-day cruise). But if you are past that you won't get anything (like an upgrade) unless you pay for the price difference - that is unless you booked through the "early savers" program with Carnival.
This is the last of the "best price guarantee" programs with the mainstream cruise lines as far as I know.
I am the editor, but I also speculate, ask questions and play devil's advocate. I reserve the right to change my mind.