The tag is present in Lintian version 2.104.328. That is the most recent version we know about.
The section indicated in this doc-base control file is not one of the standard doc-base sections. The doc-base sections are based on the menu sections but are not exactly the same.
Please refer to Debian doc-base Manual section 2.3.3 and /usr/share/doc/doc-base/doc-base.html/index.html for details.