[Ghoulish Delight]

am I seriously joining a discussion of the real-world-logistics of creating a boatplanecar?

One would presume that if the goal were to design a boatplanecar, the designers would not be limited in their design options to "okay, attach floats to this existing planecar". Just because there's no way to attach floats to the wings-as-designed doesn't mean it's inconceivable that floats can be attached and fold away with some alternate design. By your argument, they should have given up on designing the Transition. I mean, if you attach folding wings to a car, they'll block the doors, there's no way that could work.