Well, some aren’t parts of quests (explaining owl as one example). There are certainly some owls that show up on the map after you talk to them that were never a part of a quest, in my run around last night I actually saw one or two that were then added to the map, but I’d done all the quests in the area ages ago.
I also noticed that a few of the signs in Dvasia show up on the map when you talk to it, maybe it’s like that one hidden quest to talk to every sign in Siauliai/Klai.
I also do think that Sunset Flag might be part of it, given the whole “everyone on the map has actually been dead the entire time” bit… which involves all the characters from the preceding maps that the owls were involved with, doesn’t it?