The potential problem I see with changing the default behavior of systemd is that it is non-intuitive and could be potentially harmful if the user is not aware of it.  Consider the following example.  I routinely use screen when I connect to the systems I manage remotely specifically when I try to apply updates.  I do this because if my VPN connection or my Internet connection is interrupted, the update process will not die with my login session.  Incidentally, I learned to use screen when applying updates the hard way many years ago when a killed update wreaked havoc with a system of mine and I found screen to be an excellent solution.