This is true, but they are also designed with a maximum deflection for a worst case head-on crash. Typical one-rail guard rails should not deflect more than 2

This is true, but they are also designed with a maximum deflection for a worst case head-on crash. Typical one-rail guard rails should not deflect more than 2-4ft, while the cable style you see in interstate medians are designed for something like 5-12 ft. For those comparing this (EVs) to trucks, the difference is center of gravity. Even if a rail is only designed for a given weight, much effort went into containing trucks and other high center of gravity vehicles. The rail catches the vehicle and holds it down, redirecting excess energy into the ground. (Its why cable-styled rails have a gap below the top cable. Others have similar features.) But what they are not designed for is excess weight with a low center of gravity, where the excess energy just blows through the rail and can't easily be redirected in a more safe direction.