would this not suggest that they had entered my return into their computers 50 weeks after submission?
Nope. It wouldn't suggest that at all. While they may have processed the return and sent you your refund, that does not in any way mean that data has been entered into the computer system. Now I don't know this for a fact, but it would not surprise me if they had things set up so that processing is not complete until the paper check they mailed you actually clears. How they deal with it for an ACH electronic transfer, I just don't know.
