The tag is present in Lintian version 2.104.328. That is the most recent version we know about.
Debian packages should not install files under
This is not one of the
/var directories in the File Hierarchy
Standard and is under the control of the local administrator. Packages
should not assume that it is the document root for a web server; it is
very common for users to change the default document root and packages
should not assume that users will keep any particular setting.
Packages that want to make files available via an installed web server should instead put instructions for the local administrator in a README.Debian file and ideally include configuration fragments for common web servers such as Apache.
As an exception, packages are permitted to create the
directory due to its past history as the default document root, but
should at most copy over a default file in postinst for a new install.
In this case, please add a Lintian override.
Please refer to Filesystem Hierarchy Standard for details.