Yes, that’s correct. Most birds have a very poor sense of smell (exceptions being Turkey Vultures, kiwis, and a few petrels that find their nesting burrows by smell.) I doubt very much that crows are going to be able to detect the scent of a scarecrow at any distance under most circumstances.
This is more for deer and large “critters” you want to keep out of your shrubs, etc, but on Ask This Old House they helped a homeowner install sprinklers attached to a motion detection system. Once deer got within a certain distince of the shrubs/garden they were pelted with a spray of water and scared off.
Its, Eki and Fire I don’t see how that would help. I thought crows were largely carrion eaters and had no ethical problems with cannibalism.