That's surprising: How is it you can exchange a worn watch? From what I understand, an AD will accept a return only if in not worn/stickers on/not bracelet adjusted condition. Otherwise, they have to resell it as used and cannot offer it as new. Wasn't the warranty card filled out?
You're right, they do not exchange a worn watch, the dial itslef-according to the AD- can be exchanged within a limited period of time.