In my opinion the best way to avoid running XDM/GDM is simply to avoid installing it. The second best way would be to disable it in systemd. There is certainly no reason to play with runlevels when you always want to boot into the very same setup.
If you still wished to do that, the way documented by upstream is generally the correct one. Archlinux wiki is unreliable in that it can contain obsolete or distribution specific information and you didn't specify whether you actually use Archlinux. In this very case if you look in the wiki again, it now says:
systemctl set-default -f multi-user.target
This command will just create/replace the link. In this exceptional case the distribution wiki now looks more up to date than the upstream FAQ.