That's actually a pretty good summary of the difference between Upstart and systemd, with systemd your services declare what they depend on and your runlevel is now a "target" that declares that it depends on certain services. It does dependency resolution just like a package manager does.
If that were true you could never start those services in sysvinit either. It works great because there aren't cyclic references and practically no conflicting services. The dependency tree will always be pretty simple.
