The people buying these types of vehicles (cube vans) really could care less how fast they are because they know they are slow. Its a work tool, nothing more. Regardless everyone knows how these manufacturer tests go. What they didn't mention in the vid is how the GM will constantly be hunting gears because it makes most of its power up high in the rpm range.
what makes the super duty flex like that?
C channel frame with crossmembers where needed. Its better to flex than be real stiff and crack. I'll be waiting to see how these thinner hydroformed frames hold up after over a decade of heavy winters.