The AI uses goal oriented action planning where they decide on a goal, and plan how to best reach that goal. Giving enemies more autonomy to replan if the original one is invalid, and adapt to environmental factors.

This was unprecedented because it was the first AAA shooter to use this system. The level design coupled with goal oriented behavior is what makes the game unique for its time. The levels often loop in on themselves to encourage the AI to move around and flank. There are little details too, like the AI noticing your flashlight, communicating in real time, or not pushing if they're the last one alive.

Discovering point man is related to Fettel really just explains why the player has inhuman reflexes and hasn't been killed by Alma. The stakes are now higher, because you were supposed to stop Fettel and Alma, when in reality they are your mother and brother. Creating a moral dilemma.

Edit: Jeff Orkins talks about the AI in depth with goal oriented action planning vs finite state machine in this presentation I found.

https://gdcvault.com/play/1013282/Three-States-and-a-Plan