Yes, there is the hint with Min like you said, and I think it's also implied by AmRose while she has her talk with the MC in the tub that the really kinky thing that she once had to do was some scat thing. It's not very explicit, but here's the exchange:
And if you look at the conversation that the MC, Stacy and AmRose later have while driving to the beach, there's also the reference to AmRose getting 37 points by that one stunt, so that has got to be something real nasty.
So I feel pretty confident that something scat-like happened there.
But, slightly off topic, that would probably be one of the few kinks I wouldn't engage in even for points
EDIT: Oh and there is also this thing right at the end where Polly is rimming the MC on the beach and if you click on the option that it might be too relaxing, the MC says something along the lines of worrying about farting in Polly's face and that that might be interesting or something like that. Isn't really scat, but the ingredients are certainly there. So there are potentially three characters that I can see where something like that might be introduced. But I agree, that it seems most likely with Min at this point.