After messing around some more, I found I was wrong about a couple of things. So here's the updated list of things that I
think are true:
1. AI data above 'Aggressive' causes the NPC to stay in an 'alert' pose when in combat, except he doesn't do anything.
i. If package target was the player, will rotate body to keep facing the player.
ii. If package target was self, will seemingly ignore the player.
iii. Even at lower aggressiveness, there are times that the NPC will stay stuck in alert pose.
a. Unknown what causes this.
b. Can sometimes be fixed through console command 'Stop Combat'.
2. NPC goes through combat override package list once, and executes first one that matches current conditions.
i. If there is no match, will execute default combat actions, then evaluate the list again.
3. After executing a package in the override list, NPC will stay in 'alert' pose, unless the package calls EvaluatePackage on end.
4. When going through the override list again, if NPC decides on same package he just executed, will stay stuck in 'alert' pose.
The last point is what threw me off before.