Yeah, I understand the idea of not spawning in zombies for performance reasons, but if I am forced to drop into a trigger it shouldn't spawn in 3 or 4 high level zombies right on top of me alerted. I knew I was in a dangerous area, but it struck me as wrong that there was no way to get into that area (which was a closed in box) without triggering that particular fight, and it struck me as extra wrong that something spawned in right next to me alerted.
I do like the idea of "wandering sleepers" ones that aren't spawning in alerted, but are shambling around on a patrol path with more normal detection ranges instead of sleeper ones.
On the actual topic of the suggestion, I hope there is some redundancy to zombie spawning in PoIs to prevent that sort of thing from happening.