Do we know for sure that the FM tour that Stevie and Prince met on was Mirage? It couldn't have been Tusk? They played Minneapolis then, too. Otherwise I'm not sure how they would have already been friends in time for the WWD tour.
It's also worth noting that in the E017 clip, Stevie says she doesn't even remember any of this happening - that her goddaughter was there and told this story, presumably sometime after the fact. So I mean, quite possibly, by the time Stevie started telling the Stand Back story, she also didn't remember that she knew Prince before then
Or maybe the Goddaughter imagined that Prince was there.