Yeah, static re-spawns are totally fine in concept. The issue is more one of frequency and density.
I can clear a series of intersections in a city center of all (un)life, go to work on a vehicle nearby for a day or two and re-scout the same area and find multiple packs of 20-50 zombies re-inhabiting the same area already. It’s kind of obnoxious.
It’d be fine if it was just a handful of new zeds popping up, or if I was coming back a week or two later to find major spawns - but no, give it a couple days and there will often be full heavy spawns with high level crap in it like hulks, incandescents, and predators, so having to re-clear every couple days is a major PITA.
They don’t appear to be wandering hordes, as they don’t get horde markers on the map, and they don’t move much other than to chase stuff around.
Wandering hordes sweeping through I’m totally fine with, as you can see them approaching on the overmap and either decide to confront them or skirt around and let them pass by - because they are a mobile phenomena that you can see at distance, they’re much more dynamic and interesting to interact with.