No idea if its the Sapphire or not. I guess there is an assumption that it is a Sapphire because they took it to the track? In the video, that is Thunderhill West, in reverse; counter clockwise. I tried to peep the interior to see if there was a roll bar, it is too dark to tell. The biggest exterior give aways on the Air test car was the diffuser and widebody. I don't see any signs of a widebody on the Gravity in the video, and a diffuser that high of the ground is probably useless aerodynamically.
It's anyone's guess at this point.