I also like parts of AVRT, but I don't say, "I'll never change my mind". I don't think that I can know what will happen in the future. I was sober for 16 years and never thought I'd drink again. I was wrong. I just focus on now. I hope to never drink again.
However- I can see how adding that phrase might lessen the temptation to change one's mind spontaneously or on a whim. I assume that is the reason to add it.
There are many paths to recovery.