And it is supposed to work that way?! I always thought it was a bug. And probably related to the other 10+ years old acute vision bug that never got unqueued (that I remember), i.e. the way you can scan and see hidden (or even invis) npcs in the wilderness, but when you move into that room you no longer see the hidden npc (for pcs I think it worked as expected, because I can't recall any problems seeing hiding pc assassins).