Really it winds up making a big deal out of the third game of the season.
If opening day gets rained out, they're still going to play the next day; whether it was scheduled to be Game 1 or Game 2 is irrelevant.
I'll try to not be confusing here.
If the Sox are scheduled to pay April 1, 2 and 3, and April 1 gets rained out, they're still going to play April 2 and 3.
If they schedule April 1, 3 and 4, and April 1 gets rained out, they do get in all three games. But they still start the season on April 2nd.