Essentially the 1/2 choice and 3/ 4 choice are interchangeable and really don't mean much re: "ranking" the teams. ND really was the last team in, not Oklahoma. While I would agree that ND didn't sneak in, ND didn't get to be #3 strictly on it's merits.
Both Oklahoma and OSU were being sent a message by the committee. The committee had cover for their choices in that ND was 12-0 but nobody thought ND was better than OSU or Oklahoma which is what the committee says it is trying to do.
OSU was really being "punished" for the pathetic antics under Meyer. These guys knew what the story line was going to be with OSU in and they didn't what that crap polluting their big show. And since Gene Smith was caught up in the crap, it was hard for him to advocate on behalf of his school/conference. Despite a general disdain for ND in many parts of of the country, there were few squawks outside certain parts of the Mideast/Midwest when OSU was not selected.
Oklahoma, and the Big 12, was put on notice about their schedules. The committee didn't want to "reward" Oklahoma by sending them to what would have been a home game in Dallas.