That's only true if ball inflation tracks with fumbles. There have been lots of assertions that's the case, but I haven't seen any evidence.
Two counter examples:
- If you look at AFCC, that's Patriots had 1 fumble in the first half playing with an underinflated ball in dry weather conditions, and had zero fumbles in the second half playing with properly inflated balls, and in wet conditions.
- Aaron Rodgers is on record stating that he likes his footballs to be inflated as high as possible. But if you look at GB's fumble data in the link, they're #6 behind NE in total fumbles.
There are a whole bunch of confounding variables here, including coaching techniques (look at how Tiki Barber's corrected his fumble problems in one year after coaching changes).
I wonder if anyone is working on this problem?
Despite a few nit picky issues I have with this particular analysis of the Patriots fumble data it's probably the strongest evidence I've seen so far that there has likely been a persistent rules violation.