There's a sort of re-framing fallacy that comes up often in sports discussion. None of this matters because Texas isn't winning the championship.
The playoffs isn't the goal. The championship is. Arbitrarily cutting playoff qualification to #12 is required for matter of practicality. The historical and predictive chances of these late-entrants actually winning the championship is basically zero.
All this scheduling and perceived strength (=ranking) handwringing is moot. It mattered in the BCS and 4-team era, where being #2 vs #5 means a tons. Being #12 vs #15 doesn't change shit.
If Texas had scheduled a cupcake instead of OSU, but still lost to Florida and Georgia, while squeaking by Kentucky/MSU/Vanderbilt, it would meaningfully change the strength the team or its championship hopes. This hypothetical Texas team would lose to TTU/Ore in Round 1, and get assblasted by the T4 in the quarterfinals.