That is not what my department's training center teaches or LA POST. The decision of whether or not to leave the driver in the vehicle is officer discretion. There is no set standard as the decision depends on several variables.
I know some instructors that prefer to have the driver meet you at his vehicle, and then follow the occupant back to the vehicle to retrieve documents. It's part of a multi-step test of compliance. Did they understand instructions and exit the vehicle? How did they proceed toward the rear of the vehicle? Did they retrieve the insurance? And when the occupant goes to the vehicle, the officer can have him open the passenger side to retrieve the required documents, thus opening up plain view further.
There are advantages and disadvantages to each method.