I think many people report things like “I get bored with eating potatoes and thus don’t eat enough calories,” even though in principle they could eat as many potatoes as they want, spread over as many small meals as possible, and they’re clearly in a huge calorie deficit. I’m not sure how you would use these anecdotal reports to scientifically distinguish appetite suppression from “satiety” from psychological effects here. All I can tell you is that it was an unusual feeling for my appetite to go away while I was very clearly starving.

PS I’m not sure if we’re even disagreeing here. People who take GLP-1 agonists report that they’re less interested in snacks and get “full” much more quickly when they do eat, which tracks my experience on this diet. The difference is that we have a slightly better understanding of what’s happening chemically there, whereas the potato diet we’re like “maybe potatoes just make you feel really full for some unknown reason, could be placebo, shrug emoji.”