How? The fact that dynamically started services can only directly be controlled by systemd in a systematic manner is directly relevant. It explains the real difference between disabled and mask.
I don't know what you don't understand ---
"disabled" means disabled, i. e. cannot be started.
No. That isn't what it means in sysvinit. It simply means that it isn't started on boot.
> Besides, dbus shouldn't start any services, that would be insane.
You can't just deny reality. d-bus is how services have dynamically been started by a number of years. Before systemd, there was no way other way to do it.