[Chris is me]

To me, a Field Fault forces a replay because the field not operating correctly essentially means the teams on the field are no longer playing the game. The rules of each year's game define what is to be expected in each match. If the field changes mid match, they're simply playing a different game. Due to the way seeding works, this has consequences beyond just whether or not the field fault caused a loss when there would have been a win. It could affect the standings which impacts everyone at the event, and it's not fair for the standings to be impacted by sets of matches which did not follow the same rules as other matches.

By allowing teams to decline a replay you're essentially rewarding teams who find that not playing the game as defined in the manual was to their benefit. This opportunity is created randomly and not distributed evenly, so it's not fair to allow teams to decline a replay.