The tag is present in Lintian version 2.104.319. That is the most recent version we know about.
This package installs a manual page in a locale directory that includes the country name. A country name should not be included in the directory name unless it indicates a significant difference in the language. The known cases where country names are appropriate are pt_BR and zh_*.
Please refer to Debian Policy Manual section 12.1 for details.