We're obviously running into some regional differences in what defines a burnt end. I've been eating burnt ends, beef tips or brownies for 35 years here in the KC area and here's what I know from around here.
If a Q joint served me flat as burnt ends I would walk out without paying. Burnt ends are brisket point and sauce should be no where near a burnt end until its on some ones plate. Some places do serve them sauced, but those places also thow in cutting board scraps and chuck roast and a lot of other crap that isn't a burnt end, I don't go to those places (AB's).
A burnt end is a brisket point that has been removed from a packer when the flat is ready for slicing. The point is then trimmed, reseasoned and returned to the cooker until the collagen in the point makes the meat soft, tender and quite moist without sauce.