Hoping I'm missing something here. I ended up going to the bunker with a friend. Zombies (including behemoths) were literally spawning in our faces, room after room. At one point we stealthed and while it minimized the spawning it still happened. A group would spawn and ~3-5 seconds after killing the lot another group would just respawn exactly where the last one was. We couldn't do anything except kill zombies. If we both ended up randomly reloading at the same time we took a bit of a beating. Got to a room with a gun safe in it, told him to try to hold them off, I couldn't make it more than 3 seconds each attempt before I had to cancel and help kill zombies. We decided to head back to the beginning and found the entire entrance was destroyed and we had no way out except to nerdpole it back up. While there a behemoth spawned almost on top of my friend and one hit him before he could react. I was able to burn it down and get out.
I also ended up doing the research lab and did not have the same issue with spawning on top of me, though I did that one solo. Perhaps it was just a weird glitch? I did have the same issue with the entrance being destroyed and having to nerdpole up to get out. It seems like zombies above can hear me and they fight their way in behind me. I was in there clearing overnight and lot of zombies had congregated behind me since it was wasteland night spawn. Luckily I closed one of the sliding doors near the entrance behind me just in case, but the demonic ones had fireballed the stairwell/ladder area to get into the lab into a wreck. Without revealing too much the end of the lab was excellent. Took me a bit to figure out what was going on as I didn't even get to the last room and had stuff coming to me that I had to clear through to find out.
I can safely say that without getting some advice on where to find it those locations would have never stumbled across them, though I really dig the additional depth that those specific locations bring both from a narrative standpoint and a tech progression one.