[root-parent]

>> If you use the command line to do the update there is no need to reboot

Completely untrue.

And before systemd, updating sshd or cron usually meant restarting that one daemon. With systemd, core updates can affect PID 1, logind, journald, udev, user managers, socket activation and cgroup state as one dependency graph.

Before, its was replace a library and restart the few daemons using it. Now the same library may be loaded by system services, user services and systemd components, making a clean partial restart harder to verify.