Yes, the Marlins don’t hold the tiebreaker with the Sox, Tigers, or Padres, so them not playing the last game can only help them, not hurt them. So adding a loss with your scenario doesn’t do anything to the order, but you can.
But if it ends up Sox 62-100/ Marlins 61-100, Miami would have a lower winning percentage, and wouldn’t have to play to possibly get the win and knock them down the draft order. So assume the loss there, and they are 61-101.