It requires a perspective change. The documentation is not the definition of a feature. It was the spec the feature was written to, at the time work began. It is a theoretical snapshot in time of how it was intended to be implemented.

That is helpful for the future, but not definitive.

To help it out, you could add links from the documentation to release notes, PRs, maybe even the code files in the repo, so future readers can see not only what was intended, but the current reality.