Did you ask them to setup your account for you? They may have opened the box to do that.
I would have thought the account setup would be similar to the way Amazon handles the Kindle, where the serial number of a device is associated with the account, but you never know. It could also be what is holding up some people's pre-orders (including mine). If they had told me that account setup would have added to the the order fulfillment time I would not have opted for it and would have typed my email and password in myself!