TwoSix
Everyone's literal second-favorite poster
You're free to call it whatever you want, of course, but that kind of play (where NPCs operate under a DM controlled paradigm of action, independent of the players or PCs) is straight up simulationism. Simulationism really has nothing to do with the real world, it has to do with designing probabilistic rules of action and extrapolating to see what happens.Very few of the GMs I know who engage in this style even call it simulationist. That is usually a term leveled at the style from outside. But that said, this isn't even about simulating real world stuff. There are a cluster of styles that engage in this sort of thing, and not all of them are interested in portraying reality. For example there is the Living Adventure style, which was elaborated on in Feast of Goblyns and originally showcased (I believe, though it may have earlier roots) in the original Ravenloft module---going by memory here. That is merely about treating the NPCs as live actors in the game the same as you treat PCs. The Gm is encouraged to have them move around, plot and plan, and react, the same way player characters do. This has nothing to do with simulating a world. It has eveything to do with running a character focused campaign where the villains do all kinds of clever things and are not pinned to a particular location.
Random encounter charts, organized by biome? Simulationist. Weapon dice, derived from a sense of how much damage the real-world equivalent would do? Simulationist. You can't really play D&D in any form and not be a little simulationist.