I think the scent thing is pretty over done.
I don't know - certainly with roe, it seems to be make a big difference. Two observations:
I night shoot bunnies/foxes on a golf course with 3 resident parties of roe. I don't shoot them, but often bump into them. They way they react to the light seems to entirely depend on the wind: if I'm up wind, they scatter the moment the light finds them. If I'm down wind, I can walk up to within 40m with the light on constantly, and they just blink at it looking peeved.
On a farm where I stak roe, there's a perfectly positioned grassy knoll I can lie up to wait fro them to come out of forestry into a sheltered dell. The wind is very gusty and frequently changes direction. Quite often I can be lying 40-60m from a roe deer feeding calmly, the wind can swing, and the roe is off in a flash.