I'm not convinced my full-size spare will be launched so easily should my Bolt suddenly come to a stop in the rear of another car (or a wall).
My full-size spare sits pretty snug and the rear seats actually prevent me tilting the spare out of the storage area below the false floor. With the hatch closed and the rear seats folded down, I tried pulling the spare up but it was caught by the closed hatch at the largest opening. So with the hatch closed and the rear seats up, the full-size spare I have is wedged in pretty tight and can't flip-up on either edge (the one touching the rear seat backs or the one touching the hatch interior trim).
If the full-size slides left/right out of the center where I have it, it's even narrower and harder to flip the spare up. I'm fairly confident it won't launch during a collision. If anything, I'd be more worried about the watermelon in my rear seat being launched into my back or jugs of milk and juice launching towards my head since they're not strapped down either. Plenty of produce become good projectiles: coconut, apples, oranges, pineapple, frozen dinners (slab of ice), drink cans, and so on.