I have no idea what the driver's compensation is based on but it isn't transparently obvious to me that it would be fraudulent for Uber to offer me a static fare that, over the course of the ride, turns out to be different to the value of that ride to the driver.
Imagine: When I am offered a fare based on expected traffic that doesn't materialize, the miles+minutes value to the driver is well under what I paid. Other times, when I hit unexpected traffic, I pay Uber less than they pay the driver because of the extra minutes.
I'm not saying "this wasn't fraud". I'm saying, "I can imagine a pricing and reward scheme by which it's not." If at some point Uber said to drivers "We take an x% cut of the fare.", then yes, it seems clear that drivers would be defrauded by the scheme. Maybe we'll get to find out :).
edit: Other comments have links indicating that my "x% of fare" idea may, in fact, be in Uber's contract with drivers.