Those guys were writing a lot of unsafe rust and bumped into UB.

I sound like an apologist, but the Rust team stated that “memory safety is preserved as long as Rusts invariants are”. Feels really clear, people keep missing this point for some reason, almost as if its a gotcha that unsafe rust behaves in the same memory unsafe way as C/C++: when thats exactly the point.

Your verification surface is smaller and has a boundary.