Another thought -- Sims 4 has a very in-depth mechanic for abusive relationships that you just cannot have in previous games. The really only viable way to get to high-romance, low-friendship without cheating is for one or both to be abusive. I played a couple like that once and it was disturbing. I wouldn't do it again.
I'd be far more concerned about THAT dynamic than one of an angry ex confronting either their ex or their ex's new beau in an angry way. But no, let's not even think about the amount of mean interactions that require a drop in friendship that "making up in bed" and some autonomous after-woo chatter doesn't win back.
Now, to be clear, I don't think the abusive relationship mechanic should be removed from the Sims. But I also think there needs to be a lot more consequences for that scenario other than a few new interactions as well.