How long did they leave it on? Are you for sure it was salt and not maybe TQ? If it was TQ, they were creating a faux smoke ring. If it was salt, it is a theory by some to put salt on as your first layer of rub, so that the salt will work its way down into the meat acting like a dry brine, helping with both flavor and moisture, by denaturing the proteins. If you do this, it is suggested that you eliminate the salt from your rub to prevent the meat from becoming too salty.