"Is A Driver" is a calculated value based on driver selection and authorization. The checkbox is essentially being used as a 'panel expander' but with the advantage of indicating whether the person is authorized or not (i.e. two UI "birds" with one stone).
It could have been an icon and a label next to it instead of a checkbox and performed the same role of opening and closing the driver authorization panel. But that doesn't seem to add any additional value beyond what we can do with the checkbox.