I've actually taken to doing it because a few folk on the Facebook Group mentioned it. Thought I'd give it a try. When served hot the edges and particularly the fat develop a caramelized, baconesque flavour which is truly delicious. It does highlight the salted flavour a bit in the crust, which is not a bad thing if you've got the wash level right but would be awful if the meat was still quite salty.
Cold the flavour impact isn't quite so apparent, but that's possibly because the crusty texture disappears and because I slice my sandwich meat quite thin in comparison to the thicker slices when served hot.