The tag is present in Lintian version 2.108.13. That is the most recent version we know about.
Each Debian package (which provides a /usr/share/doc/pkg directory) must install a Debian changelog file in /usr/share/doc/pkg/changelog.Debian.gz
A common error is to name the Debian changelog like an upstream changelog (/usr/share/doc/pkg/changelog.gz); therefore, Lintian will apply further checks to such a file if it exists even after issuing this error.
Please refer to Debian Policy Manual section 12.7 for details.