With the whole DIO having two stands, I think it’s more The World copies the stands of the Joestars, since the tarot suggests completion and such. Plus in Part 6, DIO fixes Pucci’s bum foot out of nowhere like how Crazy Diamond does, adding to that.

wryyda:

I’ve heard that theory before, but even if it that is the World’s ability, that should not give Dio two stands. If that were the case alone, it would just mean he’d use the World to take spirit photographs but he is literally seen with hp wrapped around his hands separately 

the world’s power was originally supposed to be that you can use any stand’s power but araki changed it so honestly dio using hermit purple is just a plot change artifact, he doesn’t ever have two stands. dio also has control over his and other people’s cells that’s the explanation given for fixing pucci’s foot.