It's not common sense. Virtually all car and truck frames are made of steel. But honestly, the metal doesn't matter. Whether a pedestrian is hit by 3000 pounds of aluminum at 45 miles per hour or 3000 pounds of steel at 45 miles per hour, there is going to be a high chance of fatality.

"An IIHS study found that vehicles equipped with automatic braking that detects pedestrians had a 27 percent lower rate of pedestrian crashes than vehicles without such technology."

Teslas typically have the most advanced crash avoidance systems on the market. Virtually all Teslas have 5 star safety ratings in crashes, both in Europe and U.S. [1]

[1] https://www.tesla.com/blog/model-s-receives-5-star-euro-ncap...

Hardened stainless steel tell you almost nothing without knowing the thickness and the geometry.

At this point it’s slightly more than marketing puffery.