They probably meant things like LLVM and the various optimization passes. None of those are verified, there’s probably all sorts of correctness issues, and yet it’s still ok. Rust’s usage also has issues and bugs emitting the right intermediate form for LLVM to consume and usually also it’s ok.

Would it be nice if we had even higher level of quality? Yes. But what’s neat is we have empirical evidence - Rust code does achieve the memory safety goals over C++ even though there’s bugs in the compiler. That’s why Rust is very quickly eating all things C and C++. A huge amount of value that the industry would just be unable to access for a long time if you waited for everything to be formally proven.