They are wrongly idenfying coins right has been wiped clean which gives it a shiny bronze look.
Identity was never an issue.
And no, it has nothing to do with being wiped clean. I guarantee that given a heavily knocked around coin and an almost UNC coin (like the ones pictured), no matter how many times you wipe them BOTH clean they will still look the same. A new coin will have light reflected off the surface evenly. The more a coin is knocked around the more the reflected light is scattered thus dulling the surface. It's merely physics in action.