Why should this come as a shock?
MuckDonald's has been ripping off its customers for decades. It seems to be their business model to shortchange people. Even as a kid, I remember our family going there and ordering five cheeseburgers, and when we opened the bag there would be only four. One time we received a "cheeseburger" with no patty... just a bun filled with ketchup.
Needless to say I haven't eaten there in years. They can keep their low-quality, garbage food.