Totally agree. But is this an appropriate use for it? I regularly have to use sandpaper to remove surface rust from my SS301 knife. And I don't leave that out in the rain. It's just surface rust, doesn't damage anything, but it is rust and it's very ugly.
Thankfully with a knife, it takes two seconds to remove the rust. With an entire car? And body panels with areas that are hard to get to? Honestly if I was going to buy a cybertruck I would paint it.
If you want "real" stainless, you want 316, but it's not as strong and would require significant modifications - making it thicker/heavier/more expensive/worse battery range/etc.