I'm a main thief and i never had a problem with witnesses... the point is that you shouldn't be seen... not even by the animals

Then we disagree, because to me the point is clear. It's a bug. They appear to have been tied to an AI trait that shouldn't apply.
I expect a dog to bark, defend itself or its master when attacked, and take a dump in the street. I don't expect a dog to run and report theft of stuff in the world that has no relation to them at all.
I expect a guard to complain, defend itself or it's friends when attacked, and to try and arrest criminals they actually detect. I don't expect a guard to take a dump in the street.
At-least the guards are acting more appropriate to what I would expect (haven't seen them squat yet....)
Edited:
Fixed typo