The only thing that the server can know is whether the client has
terminated the connection with a fatal alert. If the client validates
presented cert chains, then its continuation with the connection means
that it passed validation. If the client does not, or ignores any
given error, then it doesn't mean that it passed validation.
In other words, you can only know if the client's applied policy
allows the connection to continue. You cannot know if the policy that
was applied was specifically related to the certificate chain