I am kind of wondering if it has to do with government contracts. Government contracts often are tied to inflation numbers where each option year has an allowable CPI percentage, or some contracts have terms and clauses that allow a contractor to get an adjustment if CPI is higher than anticipated.
So if the official government numbers says x happened, that's the only data the contract cares about. This would be a huge way to save money assuming you have enough vendors signed on for long enough.