I was going to say it indicates an engine starved for air.
But you are [apparently] right.
Most all of the pictures with smoke streaming the length of the vehicle show that orderly detachment. I'd like to see the smoke applied from the rear as so:
I didn't look at the pics a lot, I was mainly interested in the list of cars that have a higher Cd today. The only thing that tops it is the VW LX1 and it's a tandem 2-seater.
We have talked about this car before...
It's my favorite car. In 1974 when everyone started re-popping MG-TDs and Ford GT40s in fiberglass to drop onto the endless supply of VW chassis, it was sitting in a museum in France. The Amante was about as good as it got in that market.
If things had gone a little differently it would be as iconic a shape as the 911 and you could get them in a carbon fiber/titanium mesh today.
I'd like to see the cut line in back go more like this:
With an electic motor, you wouldn't have to worry about fumes seeping forward.
Bu, like you, I would really like to see the underside to see how Volkhart handled the airflow around the engine and exhaust.