You very rarely see this in baseball when it comes to a batting title. The batting title goes to the person who has the batting average and has 3.1 plate appearances/game his team has played (in 162 games, that's 502 PA). In rare circumstances, however, a batting title is awarded to someone who didn't have enough plate appearances, but is close enough that if you give them an 0-fer-whatever-they-have-left-to-get-502 and they're still in the lead, they win. Tony Gwynn won a batting title in 1996 with only 498 PA, for example. The more you know!
My point being, if OSU plays this weekend and loses, or even if they forfeit but officially get the sixth game, they qualify. If they don't play and end up undefeated, they don't. It makes sense in this case that they're still rewarded since they beat Indiana. I don't love that the rules are changed, and I doubt Indiana (or NU, for that matter) would get the same treatment, but it makes sense.
Now, get back to me next week when OSU has a random outbreak and can't play on 12/19.