The tag is present in Lintian version 2.104.264. That is the most recent version we know about.
The source package has a component with a very long filename. This may complicate shipping the package on some media that put restrictions on the length of the filenames (such as CDs).
Lintian only checks emits this tag once per source package based on the component with the longest filename.
Refer to https://lists.debian.org/debian-devel/2011/03/msg00943.html for details.