You nailed it. I don't think it's actually the case, but ponder this:
Luck wants his balls super inflated, so they start at 14 PSI. He's hoping the refs don't check (basically the Aaron Rodgers scenario).
The Patriots play within the rules and pump their balls in a warmer than normal room and just barely gets it to 12.5.
The balls all lose 1.5 PSI from the outside air temp being in the 30's. The Colts balls are now within range at 13 PSI, but the Patriots fall to 10.5 due to being in a warmer room to start with.