I don't see it. If you go by scores, they are similar before and after the Texas loss. Oklahoma didn't get "better" offensively. They just hit the meat of that Big 12 schedule where defenses progressively got worse.
OU came into the season with a new O-coordinator, new QB and a new O-line. Perine struggled to run the ball in 4 of the first 5 games, and the offense bogged down consistently. Changes were made following the Texas loss on the O-line, and younger more talented players replaced older guys who had been backups in years past. Since then both pass protection and the run game have improved dramatically. The offense which bogged down often early in the season has never been stopped since, except for the 2nd half against TCU when Mayfield was out, and Perine ad Mixon were both on the sideline with ankle injuries.
The idea that Oklahoma has played softer defenses as the season wore on is not born out by critical analysis.
The only way to properly judge how good defenses are between different leagues is to look at the efficiency rankings. Using a metric like "total defense" is flawed on many levels. Total defense does not account for strength of competition, or differences in the number of plays between no huddle offenses and slower paced offenses.
Many Big12 fans falsely believe that the SEC offenses are terrible as shown by the total offense stats. The other day I saw some Texas fans discussing Richt's defenses. One pointed out that Texas has played 5 top-10 offenses while Georgia has played zero top-40 offenses. Moreover, Georgia's defense got to feast on "bottom feeders" such as #88 Kentucky, #95 Auburn, #98 South Carolina, #102 Florida, #115 Vandy, #125 Mizzou....
The flaw in this line of reasoning is that total offense/defense stats don't take into account quality of competition or differences in the number of plays run. A league that is relatively strong in total offense or defense will be relatively weak in the other. It is nearly impossible for a league to be strong in both. Since Alabama plays in a great defensive league and doesn't run lots of no huddle, it will be nearly impossible for Alabama's offense to rank a the top in total offense - even if Alabama has one of the best offenses in the country like it did in 2012. Likewise, since Oklahoma plays in an offensive league with lots of no huddle, it is nearly impossible to rank at the top in total defense - like we did in Stoops' early days before the league's offensive identity changed.
If you look at efficiency rankings, you quickly see that Big12 defenses aren't as bad as many SEC fans assume...And SEC offenses aren't as bad as many Big12 fans assume.
It isn't really true that eight SEC teams have offenses that aren't in the top-70. It isn't really true that Akron has a better defense than most SEC teams, and is the strongest defense OU has played...And it isn't really true that OU faced progressively weaker defenses.
