I hunt public land and these deer are used to seeing/smelling humans to an extent. Deer have what I like to call a comfort zone. I believe itapplies to seeing people as well as smelling them. If a deer sees you (where I hunt at least)at let's just say 50 yrds, and he/shebelieves that you are unaware of it's presence, that deer will stand there and watch you pass. If that same deer realizes that you see it, that deer is out of there quickly! Their comfort zone was violated. They do know the difference as to what presents a threat, and what doesn't.
I believe the same type of thing applies to odor. They will tolerate X amount of human odor, but if they get a concentrated amount at too close a range they will break camp with a quickness because again, their comfort zone has been violated.! Just my opinion.