The bill does NOT say, Uber drivers need to change the way they work.
The bill does say, the way Uber drivers work is considered employment with respect to the law.
It changes the definition of employment to include the type of flexible work Uber drivers are currently doing.
In other words, Uber (or any similar gig-economy business) could keep working with their employees as they always have, it's just that they'll now have to provide those employees with a bunch of benefits they currently do not provide and pay a number of taxes they currently do not pay.
The idea that "employee" means particular way of scheduling hours is false. The bill doesn't say that. The law doesn't say that. There's nothing that requires that. These newly defined employees could keep all the flexibility they've had. If Uber reduces that flexibility, that's Uber's decision.