If you were to decide to arbitrarily remove 15 runs the O's would still have a +1 run differential for the season. That isn't in line with a 83-79 record.
Going back and taking an actual look at the games in September the O's lost two big ones to the Red Sox one 17-4, one 13-9. Either one of those games, if removed, would still leave the O's with a negative run differential for the season.