I finally decided to compromise the skyscraper hotel i got in my small town for some fun and fast looting before the 2nd horde. You know, that one high building with a staircase in the middle and you start from the basement, while on top you got the toughest Zs and the prizes? The staircase accessible from the ground, but blocked with a locked door and some rubble behind it, while on each floor the staircase is barred with spikes and barbed wire, so you "must follow the route" all around each floor.
Always liked that Dungeon POI, maybe because walking through it was very fun.
To my surprise the amounts of Zs in that POI were not changed. Maybe i WAS pounding on every picture (breaking glass is loud) to invoke the sleepers from time to time, but i did get like 3 Zs from a bathroom, a group laying around in one of the flats. Lastly, my favorite was a walk through flat with a hole in the ceiling, which had 3 standing up above the hole and like 5 strewn all over the flat in various poses.
So yeah, not every POI has lowered zombie counts...