The tag is present in Lintian version 2.104.244. That is the most recent version we know about.
The menu item or desktop file command uses su-to-root as /usr/sbin/su-to-root. Since sarge su-to-root is located in /usr/bin and /usr/sbin/su-to-root is only a compatibility symlink that may get dropped in the future.
Since su-to-root is now located in /usr/bin you can use it without absolute path now.