The tag is present in Lintian version 2.104.318. That is the most recent version we know about.
The package lists an old version of Emacs as its first dependency. It should probably be updated to support the current version of Emacs in the archive and then list that version first in the list of Emacs flavors it supports.
If the package intentionally only supports older versions of Emacs (if, for example, it was included with later versions of Emacs), add a Lintian override.