Those are most likely saleable cars, they have the window stickers and onstar stickers on them. Its not like they are gonna build every ordered car from the first to the last all in a row. They will build dealer stock cars along with ordered cars at the same time. They are starting slow and should be ramped up to full speed on the annonced start of production day. And I can assure you that there will be upset folks who ordered a car but then see cars sitting on the dealer lots and be pissed at how long its taking their ordered car to arrive.
Same thing happened with the Challenger guys.