I have replaced HD's in these models and then got AC support coverage. So whether it is "user serviceable" or not is a non issue apparently. Apple has never enforced what you think they would/should/can enforce. I deal with them on a weekly if not daily basis. Not really those models anymore though.
Then I'm not sure why the rMBP is being dragged into this at all. The rMBP has the same in-theory-warrenty-voiding drive swap status that other MBPs have previously had.