Luck is a top 5 QB. You know that. Good defense or not, I don't want a top 5 QB within one score with almost a half to go. That's why getting a bigger lead early, which the Bills did, makes the game way easier. A one score game means less "pinning your ears back." It means less giving them 5 yards a play and making them take a quarter to score. Basically, it means less of everything that contributed to the Bills win.
Game is in doubt doesn't mean the Colts necessarily win btw. Of course, the possibility we keep our foot on the gas would remain. But I think a 15/16-24 game is a completely different animal than 8-24. Especially with Luck on the other side of the ball.