The tag is present in Lintian version 2.104.244. That is the most recent version we know about.
This package seems to be using debconf templates, but some descriptions are not translatable. You should prepend an underscore before every translatable field, as described in po-debconf(7). This may mean that translators weren't properly warned about new strings.
Translators may be notified of changes using podebconf-report-po, for example:
podebconf-report-po --call --withtranslators --deadline="+10 days" \ --languageteam
If the field is not intended for users to see, ensure the first line of the description contains "for internal use".
Refer to Debian Policy Manual section 3.9.1 for details.