The issue at hand is less about the debian directory and more about the contents of the debian directory not being updated to follow upstream where needed. In this case the appdata was not kept up to date with upstream.
We cannot remove the debian directory from the Debian package and use the one from upstream, so if only one debian directory is desired it neccesarily must be the Debian one and Timeshift would need to stop including one with its source releases. The above is writen to give understanding to the fix that is coming to the appdata that will close this bug as the bug and its fix do not appear to align at first glance.
