I'm making a Carolina-style BBQ sauce (specifically Piedmont-style), so it's supposed to be a thin and vinegary sauce. The recipe is basically: 2 cups vinegar, 2 tablespoons dark brown sugar, 1 tablespoon each of ketchup and hot sauce, plus some salt and pepper. The instructions call for it to be brought to a boil for a minute, and then it should be refrigerated overnight.
Since the sauce is supposed to be thin, and we're only boiling for a minute, the desired effect cannot be to reduce the liquids. Is there some other sort of chemical reaction that this is supposed to produce? Also, what effect would the overnight rest have on the sauce -- I don't see the flavors mellowing in the bottle, really. I'm wondering if these are just some urban lore bits being passed down that have little actual effect on the end result.