The tag is present in Lintian version 2.104.244. That is the most recent version we know about.
If the package installs a symbolic link
/usr/share/doc/pkg1 -> pkg2, then pkg1
must depend on pkg2 directory, with the same version as
Adding the dependency just to fix this bug is often not a good solution.
Usually, it's better to include a real
directory within pkg1 and copy the copyright file into that
Transitive dependencies are not allowed here. In other words, if the documentation directory is shipped in pkg3 and pkg1 depends on pkg2, which in turn depends on pkg3, that's still an error. Copyright file extractors are not required to go more than one level deep when resolving dependencies. Each package should have a direct dependency on the package which includes its documentation directory.
Refer to Debian Policy Manual section 12.5 for details.