hmm the easiest way to explain would be example... have a friend stand a good distance behind you and throw a ball at your back ( Not of course a hard one tennis ball will do). Now their has to be some music or other noise so that you don't hear them moving ( cause in game you are far enough from the NPC they should not hear you move). Sun shining in your face, so shadow's don't give you away.
Even though you know they are going to throw a ball at you...can you dodge out of the way...if you have no idea when the ball is coming? The answer is no... for you and the Deer,, IRL... how do I know this... cause I've watched bow hunters taking down deer, hog's, turkey's ...etc. Mostly on video.. some I took myself...
NPC's should not be able to do that...specially if their back is turned,