If a team forfeits, or doesn't show for their game, we do our best to replace that team so that teams don't miss out on playing their games. This may happen before the league starts (by the office), or at the field (by a referee, umpire or supervisor). As an incentive to pick up an extra game, the game counts and can help the team that picks up the extra game in the standings.
The team would have won by forfeit does not have the option to not play the new opponent and take the forfeit win. The opponent has simply been changed.