c1ue

I understand the spirit of the statement "uninflated", but the letter of the statement is possibly not correct.
A frequent flyer on AA would earn 2x miles per mile flown due to FF program bonuses. In addition, there were frequent promotions as well as other means of gaining miles (500 mile upgrades expiring etc). Credit card spend also counted, and AAdvantage Citi credit cards have been around since at least 1998 (when I got one).
There were also promos that could be used in the past such as the infamous US Mint, the cereal boxes, etc. Not saying these were what occurred for the OP's father, but simply noting that there were lots of ways to gain program miles without BIS.
I'd lastly note that the present spend based mileage earnings, for those people like myself who never fly biz/first, make it a lot harder to earn AA miles even if they counted towards MM status.
Irregardless of the above, the fact that 10MM was reached is impressive no matter how you slice it.