[aerohead]

If we had a side elevation technical drawing of CYBERTRUCK, with it's tailgate down, and superimposed the near-streamline's smoke trace ( shown in the video ) inside the 'vault'; in theory, this 'contour' that it 'describes', would become the 'first approximation' for constructing an 'ideal' roofline contour for the truck, compared to the simplistic, 'prismatic' shape that it possesses.
It might not be 'practical' as a pickup truck, but it would be 'aerodynamic,' as defined by Dr.-Ing. Wolf-Heinrich Hucho, in the preface of his 2nd-Edition, Aerodynamics of Road Vehicles.