This makes sense to me. The player progresses through the route with the desire for the scene but the character's resistance is completely at odds with the player's goal. At least if Susan had a design that most players would find unappealing and as a result also not want to engage with her, but she has a attractive design, wants to engage with the player, and has a husband the game has made the player hate. The progression points towards one thing, but the "payoff" is something very different. (Her actions might be her unattractive aspect, but they're not strong enough to make the player not want a willing sex scene with her.)