Sure, but in Rust's case the social understanding is "there exists some type system that guarantees perfect memory safety, and has the general aesthetic features associated with rustc's type system, and 'Rust' is defined to be whatever that type system ends up being".

This is a nice ideal, but it doesn't actually exist in concrete terms as a design. It can never have flaws because the definition of it is just "rustc without all the flaws".

Haskell is in a similar boat with regards to a missing formal spec.