Do you know what the Smart pack looked like? Perhaps by the time they were asked by Elon to this conversion they decided to make a "universal" modular pack. First was the Smart, then a Mercedes (A) then another Mercedes (Models S) a supposed Magnum (supposed!) The Smart and then a RAV 4. (some order like that)
By the time you get to that last one you say, "If we are going to keep doing this we should just make up a simple" bolt on the bottom" flat modular shape."