There are many varieties of stainless.

They chose to use the same stainless as the rockets, 301, which is not the best at resisting corrosion(rust) compared to other stainless varieties like 304 that was used on the DeLorean. Had they used 304 it is likely the rust wouldn’t be anywhere near as much of a problem, the DeLorean stainless panels are still looking great and may only need a polish every few years.

Likely they chose 301 over 304 because they are already buying it for Starship and it takes to forming somewhat better.

On the plus side the steel is 3mm thick and that leaves a considerable amount of material to polish with before adding a clear coat or a clear protective film if the vinyl film coating was not chosen when buying it.