I thought the Mort bit might have been revealed to be that he planted 52 cards in obscure locations around the room and directed his firing of cards to location

I thought the Mort bit might have been revealed to be that he planted 52 cards in obscure locations around the room and directed his firing of cards to locations known to have particular cards. (E.g., down the table for hearts, behind him for clubs, etc.) He apparently does have an incredible memory. That said, the story said he did it the length of the table, which implies a more natural specificity which could either confirm a confederate, or else was retrospectively embellished. (Imagine a version of the story where he turns and fires the cards into a bookshelf and instructs someone to open a particular book.) But the confederate is a much simpler explanation. It's just whether the coordination and trust in a confederate to keep the secret to the grave can be greater than the cost of the setup and the potential for early revelation.