Comment 4 for bug 1640293

I verified this does add the targets, without enabling them.

with systemd 229-4ubuntu7:

ubuntu@lp1640293:~$ systemctl --user status graphical-session{,-pre}.target
● graphical-session.target
   Loaded: not-found (Reason: No such file or directory)
   Active: inactive (dead)

● graphical-session-pre.target
   Loaded: not-found (Reason: No such file or directory)
   Active: inactive (dead)

after adding xenial-proposed repo and upgrading to systemd 229-4ubuntu13:

ubuntu@lp1640293:~$ systemctl --user status graphical-session{,-pre}.target
● graphical-session.target - Current graphical user session
   Loaded: loaded (/usr/lib/systemd/user/graphical-session.target; static; vendor preset: enabled)
   Active: inactive (dead)
     Docs: man:systemd.special(7)

● graphical-session-pre.target - Session services which should run early before the graphical sessio
   Loaded: loaded (/usr/lib/systemd/user/graphical-session-pre.target; static; vendor preset: enable
   Active: inactive (dead)
     Docs: man:systemd.special(7)