How do you feed parts to the 3D printers? How many 3D printers do you need to make the number of vehicles demanded? How large a building will you need to house all those 3D printers, the piles of raw materials, and the mechanisms to move all that stuff through the plant?
Is it really going to take that much less space and energy than a highly efficient robotic assembly line?
The real weaselly move he makes is near the end of the article where he starts talking about the efficiency of electric vehicles and totally forgets about the manufacturing, not to mention that his first car has 700hp, which is totally over-the-top when it comes to efficiency.
The BMW i8 is made mostly of carbon fiber, has a 3 cylinder gasoline engine along with electric motors, seats 4 and costs about the same as the top of the line Tesla. It could easily be built with 3D printers and probably will be.