A Cold nosed dog is simply the one that can consistantly take (and jump) the oldest tracks. The dog that can start a track that others can't. Now if it takes more desire, brains, scent receptors or a 5th leg it doesn't really matter to me. I just try to find the ones that do it the best and then maybe see if a pup out of them can do it. There isn't any real rocket surgery behind it.
One thing that seem to add up is that you'll get more cold nosed dogs out of cold nosed parents. I don't think all will, but it seems that your odds go up. Just the law of averages I would guess.
On your original question, I don't think all dogs can smell the same. 1, it's impossible to prove until dogs learn to talk



