I'm from another forum than this one, and I can say both parity games and inevitable elimination games are normal. It's not some quirk of ZD specifically.
The important thing is that the scum wincon was given to the players: "You are with the Mafia, which means that you win when nothing can prevent you from eliminating all of the other players."
This was supplied to the scum players when the game began.
I haven't looked at the roles yet, but the game was—in theory—balanced around this idea. Roles that would have been hard to deal with in endgame needed to be dealt with using appropriate counters, lynching, or trading and single scum bus strategies lost a lot of power. Both minish's and my role were hazards/eliminateable by the SK and the vig as well.
This is a rule that makes victory harder for scum, but things like claim limiting, flavor claim banning, and lack of most meaningful role information on death made this game more difficult for town as well. Different rules variants can effect balance in different ways
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Personally, I view this game as an unofficial victory for Sun Sun and a tie for town/scum.