If drivers keep getting requests cancelled, they will be less prompt and enthusiastic about actual ones. The cancellation fee is calculated on the assumption that frequent orders will not be deliberately placed to be subsequently cancelled.
I agree that they may have violated the spirit of the contract. But the contract specifically handles the case of cancelling an order (including some restitution), so I would hardly consider it fraud.
They claim they paid cancellation fees. Gett claims the charges are pending. At this point it would be stupid of them to not let those charges through though.
If Uber wasn't a douche, they would have just booked rides in the cars and personally talked to the drivers. Absolutely no harm in that. What they did shows an utter lack of tact.