all they had to do is flatten images and restamp
So what they would have to do is take a 1942 cent which is already the exact size of the hole in the collar, try to force it down into another collar (not an easy thing to do, that's why planchets are slightly smaller than the finished coins, so they will drop into the collar easily.) Then stamp it with blank dies to flatten out the previous details. Push it out of the collar. Force it back down into another collar being careful to keep it lined up exactly with the 1944 dies, and strike it again. Obviously this is not something that can be done by machine, each coin is going to have to be individually worked down into the collars and then struck. Can you really see them doing this?