“If all the tied teams are not common opponents, the tied team that defeated each of the other tied teams earns the Championship berth.”
As George Stoia of On3’s Sooner Scoop pointed out, the original tiebreaker rules did not have that sentence in there. The language has been added to Step 1.
There’s a bunch of teams at the top vying for spots in the championship game, and there are possibilities for ties. Some combinations of W-L to close out the season had certain assumed tie-breakers to get to the championship game, but this “clarification” breaks some of the assumptions. The statement by the Big XII acts as if nothing has changed, but it looks like they added qualifying words that weren’t there previously in order to make this clarification.