The tag is present in Lintian version 2.104.244. That is the most recent version we know about.
The upstream source contains an .svn directory. It was most likely included by accident since Subversion version control directories usually don't belong in releases. When packaging a Subversion snapshot, export from Subversion rather than checkout. If an upstream release tarball contains .svn directories, this should be reported as a bug to upstream since it can double the size of the tarball to no purpose.