Didn't Romo have a better rating than Rodgers in the playoffs last year? 143.6 to 125.4
The concept of the team with the better passing differential wins is an 80% concept, IIRC. It's not a 95% type of thing.
Where the entire theory goes off the rails is when people try to use it to make conclusions about the running game. The threat of the run improves passing effectiveness but people that promote the theory can't or won't acknowledge that fact because they can't measure it.
If a defense faces two offenses and both offenses gain 50 yards rushing but the defense played 7 men in the box against 1 offense and 8 men in the box against the other, the
stats make it appear that both teams had equal running games; however, that is far far from the truth. The offense that faced 8 in the box had 1 less defender in coverage against the pass. The threat of the run therefore helped that team's passing effectiveness. I say threat of the run because you can't use rushing success as measured in yards because the defense adjusted to limit those.
The 7 vs 8 in the box is just a simplistic example. There are obviously many ways that defenses adjust to limit the running game at the expense of their pass coverage.
I think the Passing Effectively Differential = Wins is more of an effect not a cause of winning. By the end of the game, most teams that win will have a better passing differential than the losing team. Considering that the stats only support it at about an 80% rate makes the whole thing of minimal value.
Considering that most teams have around 400 yards of offense in a win with 300 passing and 100 rushing should make it obvious that rushing as measured in yards is not a good stat for comparison. If one team has 50 yards and the other has 100 yards rushing that 50 yards is not a big percentage of the overall 400 yards gained in the game. That's 50% more rushing yards but a 50% better day in terms of passing yards would be 150 yards for the loser compared to 300 yards for the winner. Obviously when using the stat yards, passing will correlate more than rushing just because of how the numbers work out.
The value of rushing is not the actual yards gained because the defense can adjust to limit those. It is in how the threat of the run affects the passing game and how a quality running team has an advantage in various situations like short yardage, goalline, less predictability, etc..
Another reason the stats are off is because of what happens in games where there is big difference on the scoreboard in the 2nd half or 4th quarter. Teams that are winning will often run the ball for a low average per carry while just running out the clock. Teams that are behind often throw caution to the wind and just start throwing the ball around in a desperate attempt to score in a hurry. Passing in this situation will obviously not be efficient on average.