And such a spec can be 1) a reference implementation, 2) written in natural language, or 3) written as formal semantics #1 is the same as the current situat

And such a spec can be 1) a reference implementation, 2) written in natural language, or 3) written as formal semantics #1 is the same as the current situation. With #2, you might get a bit closer but natural language has many ambiguities and idiosyncrasies that can render it useless in various situations. You can try to define formal semantics, but that is not only hard to create, it's also hard to translate into an implementation, adding significant overhead in both parts of the process. And there can still be bugs, and there can still be edge cases with undefined behavior.