The tag is present in Lintian version 2.109.24. That is the most recent version we know about.
This non-native package makes no changes to the upstream sources in the Debian-related files.
Maybe a mistake was made when the upstream tarball was created, or maybe this package is really a native package but was built non-native by mistake.
Debian packaging is sometimes maintained as part of upstream, but that is not
recommended as best practice. Please make this package native, if the software
is only for Debian. Otherwise, please remove the
from upstream releases and add it in the Debian packaging.
Format 1.0 packages are subject to the restriction that the diff cannot remove
files from the
debian directory. For Format 3.0 packages, the
debian directory is automatically purged during unpacking.