waystone map mobs not respawn after killing boss

So I was in some bog map where there was an (ice) witch as unique boss.
It was in area of its own differentiated as new room/ area/ subspace then the rest of map and mobs.
So I killed my way into the area, entered the arena, died, got notification that upon death on unique boss all mobs respawn and respawned at checkpoint outside of arena, entered room again, Killed witch.
Now upon death the arena merged with the rest of map.
I ran around looking for mobs but the map is clear so idk if its intentional or not, but there are no mobs, or maybe its kind of different instance cuz there was no transition.
anyway im giving heads up and anyone who is looking into it good luck! :)