same here.
It's likely down to a basic coding error --
an enum list starts at 0, but the victory screen code starts at 1, meaning that 'impossible' is actually a 4, but the screen uses 5.
I back that statement up by people stating that a 'challenging' game shows 'impossible' on the victory screen and 'normal' shows 'challenging'.
-- the code is off by 1 each time.