Simple fact...there is nothing in the rules to support a continuation of the game at a later time if a half has been completed. It's unfortunate for the team that is down a goal, but the rule is that if the game is called due to unplayable conditions PRIOR TO the half, it will be resumed at the point of interruption. After the half, the game is considered complete.
There have been plenty of games that could have gone either way that have been decided early by weather. I've been in a few, on both sides. Again, it's unfortunate that it happened in the playoffs when it's win or go home, but how is that so different than if it happens in a region game that determines whether you get there in the first place, or who you have to face?
Again, an unfortunate circumstance for the team who is trying to equalize, but the rules are very clear. It's not a matter of how close the playoff matches are scheduled together, or transportation, or inconvenience. Scheduling the last 20 minutes at a later time would have been a violation of the rules and procedures every SCHSL team plays under, and would have given the benefitting team an unfair advantage over every other team that has had a close match shortened by the same rule.