I guess if ignorance of the way he's hurting people counts as "not cheating them" this is true.

He gets the airline miles because the US mint takes in between a 1% and 3% loss on the transaction to pay the credit card company. They also lose money when they ship him the coins for free. The reason the US mint is willing to do this is because coins are so much cheaper for them in the long run than bills, once they go into circulation; they're paying this guy and UPS a fee for helping them put dollar coins into circulation. This guy is taking that fee, but not putting the coins into circulation. Its not like the money in his rewards account appeared out of nowhere.