In the article it states that drivers have been fired for not taking a certain percentage of passengers. While it isn't a strict hours, it is firing someone for not meeting their determined amount of work.
As she says these companies are square pegs that are trying to be forced into round holes. Uber drivers are not normal independent contractors, but nor are they full employees. I really like Uber, but forcing employees to pay for gas, maintenance, insurance, etc is abusing their position. There needs to be a reclassification that can work for the on demand companies. Place these employees somewhere in between and require certain things be met, maybe pay for gas whilst they are driving passengers, or a stipend for maintenance costs.