I think the two parts of this statement can be decoupled. Couldn't Uber feasibly keep fixed upfront pricing on the customer side but provide variable payouts to drivers to be compliant with the law? They probably wouldn't do this because it exposes them to risk on every ride (i.e. they might undercharge for the ride and have to pay up to the driver anyway) but the law is not directly forcing them to provide a worse experience - they're doing that by passing the risk to customers.