So I just want to add to this. I noted the same before the latest update and have now installed the latest update and NPCs now spawn in a base however there appears to be an issue now with the correct number spawning outside IF any are set to spawn inside.
Example:
On extreme bases I ahve a total of 12 scientists and 10 murderers set to spawn and if I do not set any to spawn inside, they all appear roming around outside.
If I set to spawn just on floors or rugs for instance and limit inside to only 4 scientists that should leave 8 that should appear outside however I see none outside and only murderers