When I saw the title, I thought that he really meant specialized. A specialized driver is a driver that can and does haul ANYTHING ANYWHERE. Van, flat, tanker, reefer, OSOW, cars, hopper, hazmat, double and triple pup...etc.
I call that an "experienced driver". When I think "specialized" I think of someone familiar with 13+ axle super-heavy haul platforms, and all that goes with those very unique jobs.