Correct. However, the $50 refund is not something that can be processed at the gate, unfortunately.

I like the case where one is upgraded into F, confirmed, then bumped back to Y due to a late connecting passenger. That indeed is an IDB since the text of the law is that you're due $$ if not seated in your confirmed cabin... have never had it happen myself, but if I did, I'd ask for the IDB credit.