You do realize it was pouring rain and the footballs were soaked during the AFC Championship game against the Colts in 2015, right?
And that the game between the Steelers and the Giants was dry, right?
It makes a significant difference. Wet footballs vs dry ones?
Exponent made detailed measurements of a football's bladder when both wet and dry. The difference is so small, it is within the uncertainty of the measurement devices.
A bigger difference would be the change in atmospheric pressure during the game. During the first half of the 2015 AFC Championship game, the atmospheric pressure declined by 0.07 psi. All else equal, this would increase the measured pressure of the ball by 0.07 psi. (Think of taking a bag of potato chips to a high altitude. The decrease in air pressure makes the bag puff out.)
During the December 4 game in Pittsburgh, the atmospheric pressure declined by 0.03 psi. The change in atmospheric pressure is more statistically significant than the impact of a wet football.