I have a theory about how weirdly human the NPC’s are.
Aside from the written storylines, I think the company that runs the game has people playing the NPCs. They only tell them the information and background that their character should have, and then some basic outlines of quests they can or should give. Then the world building can be extremely advanced without having to develop AI’s.
Though be technology does seem to be so advanced that it links right into the brain, so who knows. 1/2 Prince explored the idea of super realistic AI NPC’s so I’m not averse to this showing up here too.