GM had to design the Vega so it wouldn't leak gas and other fluids when spending days (weeks?) nose-down in the Vert-a-Pac. IIRC there were plugs that had to be inserted. So yes, GM, was involved with the shipping design as well as the car.

Teslas still have fluids - the coolant loops for the various bits - that would have to be designed for proper retention when spending an indeterminate time nose down. And that battery is *heavy* - the Vega probably weighed roughly the same for the whole car as just the battery in a Tesla Model 3 weighs. Finally, does Tesla even ship by rail? My impression is that everything at their factories enters and exits on trucks, even if it's right next to a rail line. Tesla deliberately removed all of the tracks that once entered the Fremont plant (when operated by GM and Toyota). So if they're shipping by rail now they have to first truck the cars to a suitable ramp.