Be real with yourself, would any AAC team be ranked with Oklahoma state's resume? You can't look at their 'sos' because it is inflated by biased rankings. Realistically, they have had three tough games at 8-2 (beat WVU, beat Pitt, and lost to Baylor). It actually is pretty solid, but they also lost to Central Michigan. The rest of their wins are nothing to speak of, unless a one point win over Texas Tech is a "good win". That puts them at #11
Now, look at Houston. They have also pretty much had three tough games in Navy, Oklahoma, and Tulsa (you can say they aren't good all you want, but they have been unranked / receiving votes all year just like Pitt has) they went 2-1 in these games as well, and had a similar head scratcher to SMU (though I would argue SMU is slightly better than C Michigan, but not by much).
Though the resumes are not far off, Oklahoma State is #11, Houston is completely unranked. Thus, there is your biased rankings.
Top of the AAC = Top of the Big 12