The very notion that one has to pay more for not taking advantage of the full services already purchased appears so strange to me that I'm not really surprised that this is not written down.
Admittedly, the courts in Germany are much more on the consumer side with their rulings than are courts in the US, but I'd still find it strange on what basis the airline would want to claim more money.
Indeed.
There was a Supreme Court Justice (Scalia maybe?) who made some sort of reference to throwaway ticketing. It seems he would vote to allow it if it ever came before the court...