Interesting point I might bring up. When I did my MECIR just over a year ago, I was taught to make sure I reported when changing to the CTAF and that it was courtesy just to let them know I'd continue to monitor Centre/Radar as well and it always made sense to me. As my instructor at the time pointed out to me, I have 3 comms, most IFR aircraft have at least 2 some that can even monitor 2 frequencies at the same time so why not just keep it on in the background incase something important comes up and let the controller know that in a real emergency he would be able to get ahold of you?
Yes its not by the books, makes it "Non-standard" but as I was also taught, sometimes its easy just to use plain english and get the message across clearly than trying to always be by the book and not get your message across?