They had this in Baldurs Gate ToB (iirc) as a joke. Your high level adventurer party stumbled upon some other party of low level - which attacked you on sight. After you killed them all there was a message "xxx reloads", they re-appeared and were really really friendly and accomodating. Regarding the mechanism: I highly dislike it. There is already a warmonger penalty, the other victories should not lead to increased tensions. It destroys the immersion of the game, all other modifiers have an explaination (promise kept, agenda, gift etc) but "you are winning" is not something the leader of the AI should be "aware" of. Behind the courtains it would be fine if they would collobarate to stop you, but this mechanism is just making the bad diplomacy system worse.