"I have zero faith in the courts’ ability to distinguish this. In the case of Uber, their business is providing the back-end, and their revenue is a commission for doing all the back-end work. They are not in the business of driving cars — no Uber employee drives a car — and yet this bill would make the car drivers employees."

I find this an interesting interpretation of how Uber defines their business. If Uber only provided the back-end for their work, the common consumer wouldn't know about Uber, you would know the driver directly and reach a deal with the driver directly. I would relate this most closely to things like in China where you can pay via WeChat or elsewhere with Square where they just facilitate the transfer of funds. They would be a distant party to the work actually being done.

Instead the average consumer knows Uber, goes to Uber with the goal of fulfilling their need of getting personal transport door-to-door, and the act is delivered by their contracted driver. They expect Uber to handle the complaint escalations, money handling, route planning, and basically everything related to that goal. If Uber provided only backend you could create your own frontend/theme to Uber for your local town (like you would a wordpress for a SMB) and create a business around just that. While there may be some back and forth on interpretation I think the real test is that based on all those steps that have to happen if the ride itself was omitted from all the services they created would Uber still be able to function and the answer is no which would make it part of the "usual course of the hiring entity's business." If Uber (not counting their other lines of business) didn't actually arrange rides for people, they aren't a company providing a marketable service anymore.