The panels on this "slug" (think fake quarter to test coin machines) have not been trimmed out. Its clear this is an assembly test run (for clearance maybe?).. I think thats been echoed by those who work at the plant already. My 3 cents is that this car (slug) may not be testing the entire line so don't expect it to have all of its " boltable sheet metal" including space for the read end attachment. I wouldn't expect much from this... clearly it shows what the exterior mold and lines will be.
Here is evidence.. the sheet metal for for the tailights, headlights, rear valence clearance and front clip have not been trimmmed from the original stampings. There are no clearance or install cut-aways, not just for wiring. UNless GM does it differently?