> Usually the standard comes first, compiler vendors implement it, and between releases of the spec the language is fixed.

This is not how C or C++ were standardized, nor most computer standards in the first place. Usually, vendors implement something, and then they come together to agree upon a standard second.

When updating standards, sometimes things are put in the standard before any implementations, but that's generally considered an antipattern for larger designs. You want real-world evaluation of the usefulness of something before it's been standardized.