Possibly. That still wouldn’t explain how I have 6/7 completed when there seems to be only 5. Which is why I wondered whether the intro race counted as a Showcase. Then there’s the disparity in the stats where it says I’ve won 4/5 Showcases. So only 5/7 are winnable? And I’ve no way to readily tell which one I didn’t win.
I have the same problem as your bolded text. Is there a way to check which of the 5 you haven’t won? All my Showcase map icons are gold; shown as completed.