I had always assumed that vinegar was, in fact, used in the production process somehow or another. Reading that it isn't, I can accept the smell is caused by something naturally occurring, I see no conspiracy there.
I am surprised, shocked even, to hear folks say that there is no scent at all. I can assure you that it is not simply the power of suggestion with me. My first tinned tobacco was Blackwoods Flake. I was expecting something sweet and sugary (something along the lines of a cross between PA and CBW). When I popped the tin, I immediately ran to the internet thinking there was something wrong with it. Someone explained to me that the worse it smells, the better it will taste, and it sure seems like those are sage words. To this day Blackwoods Flake is one of my favorites and I keep multiple tins on hand at any give time and it still smells the same.
Ok, so maybe its not a ketchup smell per se, but there is definitely some sort of vinegary/ ketchupy/ BBQ Saucy thing going on. But whatever it is and for whatever reason it is present, I'm fine with it. It could be magic fish urine and I still wouldn't give up my beloved Blackwoods Flake.