Just here to be one sample point. I have been with an average number of women. My girl now is slim, and so I come here to solely to lurk and feed my fetish. So I don’t think fat admirers are all incels, but I’m just one counterexample so I can’t say whether the majority are.
I think I’m about average looking (maybe Just below), but I am a smallguy (5’ 8” 140lbs). I actually have a way easier time with shorter smaller ladies. I have been rejected by many pretty-face large girls I wanted because they felt even more self conscious with a guy my size. Except in the case of seriously desperate girls, I truly think you may have that part backwards for the population you’re interested in. The good looking curvy girls would prefer a bigger male, even if the guy is a bit uglier.
Side note, I am black so there may be some kind of exception and your analysis may be accurate for whites or others.