What
When a local server response includes the version header, it now also sends Vary: User-Agent. This header tells anything that caches the response that it can differ depending on which program asked for it.
Why
It stops a cached response meant for one client from being handed to a different one.
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
The finding does not say which local server this is.