I don't know either, it is an arbitrary determination.
I'm a driver, I like driving my Impreza, therefore my Impreza is a drivers car.
Whatever. Just drive it. If you want to control the behavior of the car and not let it make more choices for you, get the standard. Because it is quirky, you will have lots of fun learning how to wring out its optimum capacity. But its what makes a Subaru, a Subaru (at least this one...)