I seem to remember there were some situational factors in play. Texas A&M had played Kansas 5 days earlier. Worst defense in the country, virtually the equivalent of lining up against air. Then less than a week later they are asked to face the one Big 12 team that makes a legit attempt at pass defense...actually varying the number of pass rushers, disguising coverages, and occasionally attacking the underneath stuff. More or less unfair, in the cupcake Big 12.
I have a buddy in Las Vegas who prioritizes situations like that, a team that is suddenly facing a defense dramatically better or worse than a week earlier. Such a simple term, in blowhard friendly Las Vegas sportsbooks. He'll walk up and say, "Texas A&M...uphill," or "USC...downhill." He looks to bet against teams in uphill spots and with the teams in downhill spots. I must concede I wasn't a full believer until he spent the entire two weeks before the 2001 Super Bowl smugly chanting, "Giants...uphill." New York had hosted a weak Vikings defense in the NFC title game before being devoured by one the terrific historical defenses in the Ravens.
The theory is it's too much of a shell shock for the uphill team to adjust. Plays that were waltzing uncontested a week earlier are stuffed. No matter how well prepared you are by the coaching staff, it's natural to be full of yourself after an offensive breakout, and expect a rerun.
If we draft Tannehill or Weeden, it's uncertain how they'll fare against NFL pass defenses but I guess we hope to avoid the University of Texas. The combined YPA against the Longhorns was roughly 5.0. Weeden, like Tannehill, faced Texas one week after feasting on Kansas...uphill. He actually was fortunate in the 4th quarter when he stepped out of the end zone for a safety while throwing a pass that was pick sixed. Ouch. Spread was +9. A TD would have cut Oklahoma State's lead to 7 but the safety maintained at 12, and that's where it ended.
In regard to Tannehill vs. Texas, keep in mind it was also the end of a disappointing season for A&M while Texas was still perky after shockingly missing out on a bowl in 2010. Also, in the final meeting of the two programs before A&M departs for the SEC, the blue blood program had considerably more at stake. It would unnerve Texas fans beyond description to lose the final meeting with the "joke" Aggies. That's simply reality. A&M may have wanted it but Texas was desperate to preserve the pecking order, to have the final say at every subsequent water cooler discussion. Those type of variables contribute to one side exceeding expectation. I distinctly remember how Texas players raced around the field in glee after surviving that game. I'm not exactly thrilled with Tannehill but he had some factors working against him against Texas, basically an opponent with greater intensity level.