Short answer: It's not the deer. You're doing something wrong.

Long answer: The deer are absolutely *NOT* coded to dodge projectiles. They either saw you, or heard you, and it's just a coincidence that they moved as your projectile got close. I've pulled off hundreds of stealth kills on deer with bows and they simply do not dodge at the last second. If they were coded to do that I'd have seen it at least a few times and it just doesn't occur.

Deer are ridiculously easy to kill in the game once you understand how to properly hunt. Once you get the hang of it you'll rarely miss and you can actually get close enough to melee them if you know how.