areas respawn enemies you've already killed after you leave and come back
So exactly like SoC.
Simple example. First combat encounter, ATP on Cordon. You clean out the bandits and stolkers move in.
The new bandit team will spawn somewhere on Garbage and will move to ATP in 12-24 hours. If you are still on Cordon, you may see them getting in combat with other stolkers, animals or military. If you are not around, they will successfully reach ATP and reclaim it - not because of predetermined outcome, but because they simply outnumber stolkers. If you remain with stolkers and skip time somewhat, you can help them to defend.
A lot of this happens especially in the Garbage, it's constant tug of war between stolkers and bandits.
And so on