My guess is that most of those cars are destined to be assigned to various GM employees (like the ones already assigned to Scott, John, and Cheryl, as well a black 2SS/RS assigned to some powertrain engineer that lives in my area ).

 

Hrm was hoping to peek a CGM in there somewhere!
Maybe if i squint one of the black ones will look gray

 

As others have said, they won't be building those for another month or so.