Well, I said the case design might be different for the high-end set. I can't say with 100% certainty, although from what I have seen the jewel case for the regular, Limited Edition and Legendary versions of the game appear to be slightly different from one another. In any case, I seriously doubt every copy of the game would be scratched. Microsoft wouldn't have put all that money into development if it was going to result in many customer complaints and returns. Not a very sound marketing standpoint, imho...
EDIT: From what I read, the Legendary disc set either comes in "a tweaked regular edition case with the old school clip to hold the disc" or "two black plastic DVD cases." So, anyone who bought the high-end set needn't worry about this problem...