Certain exhausted topics can be highlighted again even though there's no new dialouge

Activate an NPC and click on a topic that's colored (like latest rumor topic), click on "background" and the topic that was clicked before that and exhausted will get highlighted again but the answer is already heard (there's no new dialogue), expected behavior would be if an answer is already heard the topic would stay greyed-out.

But if a topic was exhausted before activating the NPC (opening the dialogue window) then it won't get highlighted again as expected, an example, if I click on "greef" (an already greyed-out) topic then click on "background", the topic won't get highlighted.