Perhaps the difference is you told the group of workers “I want trees A and B trimmed in this way”, but you probably weren’t saying “Tom, I want you to trim tree A, Dick, I want you to trim tree B, and Harry, I want you on the ground passing tools up to Tom and Dick as needed.”

Your example sounds exactly like a statement of work in a contract. My example reaches past that into the company to manage their use of labor.

This doesn’t necessarily apply directly to Uber because they may argue that they are contracting a single ride, and the driver/contractor is fulfilling that small contract in any way they see fit.