All reports of udeb-uses-unsupported-compression-for-data-tarball for the archive. The extended description of this tag is:
The data tarball of this udeb package is not compressed in format that udpkg (debian-installer's dpkg equivalent) does not support. Thus the udeb is likely to be uninstallable and could break daily or weekly d-i images.
Currently, udpkg supports .gz and .xz compressed tarballs.
This tag has not been emitted in any package tested by Lintian.