Yeah, good question. With this brass, it was pretty obvious after running it through the FCD that it had been smiley-ed and resized, see pic below. With less of a smile though, it might not be noticeable. Or, maybe people just think it's re-usable anyway.
This isn't the best picture, but the brass is shiny from resizing above and below the smile, but the smile is still visible. This chambered just fine before sectioning. This is the piece of brass in the second picture above.