They are none of those...
...but rather are drawing a distinction between processes and daemons:
"The reality is that if you're expecting processes to run after you log out, you're not using systemd right - and indeed, you're not using your *nix system right at all... ...If you want a process to carry on running after you log out, you have systemd look after it as a daemon"
In other words, processes, which are initated by the *user*, should be stopped when the *user* logs out.
If you want the process to keep running, it should be run as a daemon where it has reduced privileges, can be managed by the *system*, and can therefore still be managed when the *user* has logged out.
This is an important distinction that has been missed in both the article and the discussion that it seems systemd is only killing user processes on log out, not system deamons. This is how I would expect any OS to work, and indeed even Windows will do this.
I am not a fan of systemd; I dislike anything that unneccessarily obfusctaes itself behind binary blobs (grub2, I'm looking at you...) but if one looks at this rationally instead of emotionally (maybe a difficult thing where systemd is concerned) then this is really expected and sensible behaviour.