I believe the justification, in the report, is that Anderson was unsure of which gauge he used but believed it to be the Logo gauge. Further, because the Colts weren't being investigated the data lined up with the non-Logo gauge being used initially, since the psi drop in those balls more aligns with the non-Logo gauge readings at halftime. So they used the non-logo numbers as the more scientifically plausible.
Two major flaws with these assumptions:
1. Where and how were the Colts balls prepped? Belichick gave a detailed accounting of the Patriots prep, but what happened with the Colts balls, at what temp were they pumped up at? Did they come in from the team bus (or the field) minutes before they were tested pre-game, thus reading artificially low (and closer to their mid-game reading), which would make the Logo gauge the one Anderson likely used? Maybe some of this is in the report, can anyone who's been brave enough to read it cover-to-cover let me know?
2. Speaking of the ball prep, what about Belichick's presser where he discussed their pre-game ritual? The artificial inflation of ~0.5 psi due to the rubbing process...I know Exponent did a side study on the effects of rubbing on the footballs but it never seems to come up when comparing psi's. What if the footballs the Pats used had an 'equilibrium' state indoors of 12.0-12.1 rather than 12.5, wouldn't that fully explain the non-Logo gauge readings?
In both cases the observed data would completely align with the science. Further, I have a very hard time believing that McNully (and Brady by extension) would risk a monster scandal over .3-.4 psi...that's seriously what they're hanging their hat on, literally the effect of putting the needle in twice--not even deflating but the natural effect of putting the needle in twice is what McNully/Brady are guilty of. INSANITY!