I was so disappointed when TAC went down this route. There is no reason for Anne to be voluntarily screwing her wrinkled pervy neighbor, no matter how big his dick is. Ditto the doctor, the plumber, the boss' teenaged kids (and they're teenagers, let's be real), and so forth. This isn't one of those RPGM Bambi in Lechertown games in which Anne is being blackmailed and raped and corrupted by everyone she meets. She's choosing her partners, whether or not Tony's encouraging her.
It's one of the big reasons I liked the sharing route in Deliverance. Everyone's on board, no one's cheating, the wife's extramarital partners are all people she could reasonably be attracted to. And you're right: the number of games where this is true is vanishingly small. It's been a long time, but didn't A Happy Marriage fit this bill? My Wife's a Star definitely doesn't fit this paradigm, alas.