How can something be referenced with out showing up? When it is used for an easter egg, fan service, or reference it is required to have shown up in that medium. Otherwise it wouldn't be a reference, easter egg, fan service, etc because it wouldn't be present. I'm not conflating food with meat. Again you create a strawman.
Your question is a red herring. It doesn't matter if things can be explained otherwise. What matters is that he had knowledge of the future but it was not wiped in order to keep canon. I'm not sure why you are missing that key detail and reason for it being brought up. Yoda had visions of Order 66, the younglings being killed, and even says to Mace Windu and Obi-wan that the war is lost but the future can still be won. He was using what he learned to play 4d chess to defeat the emperor.
The writers could have done the same with Mortis. Incorporated it into the story both past and future. They chose not to by doing a partial memory wipe. It wasn't a memory wipe, in the story, because the writers had to follow canon of the OT. There are plenty of different ways they can approach things and still have a character arrive at their original appearance.