Samseb, one doesn't need to completely understand exactly how each part of the brain functions to be able to apply AVRT. By Trimpey's own admission, it's a very simplified model of how the brain works. The key for me was the split, because much like the Buddhist approached to dealing with hindrances, AVRT teaches the split as a technique enabling one to become the observer of the desire or craving, to stand at a distance and not act on it, but rather watch it come, watch it go.
For me, the purpose of the approach is not to actually believe there is a beast, or to think I'm literally of two separate minds, but rather a technique (the T in AVRT) for stopping a behavior. It's actually an age old technique. Trimpey tweaked this approach based on what he learned from the self-recovered population.
To the OP, yes I'd say it's been effective for a great many people. What that number is, I have no idea. And personally I'd say Trimpey is a bit of a weirdo, but I don't see him as "anti AA" just to be a big meanie pants. He very sincerely believes that there are flaws in popular recoveryism that keep people addicted. Since he believes this is a serious problem, it's not so shocking to me that he would speak passionately against it.
But hey, it's a book. It's not going to open itself and position itself in front of anyone's eyeballs. Trimpey himself says no one need avail themselves of the technique if they don't want to.