The comment posted by jamesmunns will do much better job in describing the exact details than mine (both comments happened to be posted within 20 seconds, huh), so I'll just add that standards are meaningless by their own. Quite a lot of people criticizing Rust for the lack of formal standards seem to assume that such standards will immediately improve something, but that's never true. Standards are meaningful only when they are maintained and can be enforced; many historical standards failed to catch up and fell into the oblivion for this reason. It doesn't even matter much whether the specification is written in "formal" prose [2]. I feel they are missing the fundamental reason why language standards can be beneficial in principle.

[1] https://spec.ferrocene.dev/

[2] Which is never "formal" in the mathematical sense. (Mathematically formal language specifications are quite rare, examples include SML and WebAssembly.) In fact, such formal writing is slightly better than informal writing only because such writing also aims to be unambiguous, and the formality itself is not that important.