Yes! And not even a lie to Dean- in IMTOD, he tells John "I can't, but I know someone who can," and has to possess a Reaper to get Dean back! And Dean wasn't even properly dead yet. Now, they may well have been some kind of analogous back-scenes dealing going on here that the YED just didn't reveal to Mary, but you could drive a Pinto through that monster-powers-inconsistency.