For good reason and a way to solve lag issues. Optimization options where you could adjust based on difficulty/lvl.the types or quality of enemies that spawn as well as how numerous.
Like low level areas could be adjusted by the player to just have hunters and dogs. Or any other combo ectc. Based on player preference. Of course there would be limitations on it. And scaling . But itd be set up to allow Optimization of spawn rates for frames.
Also. Options to turn down the frequency of tracer rounds. Adjust render /load. Ectc.