Not completely but kind of, all those poweroff, reboot etc. tied to systemd, though I believe this is mostly related to polkit run out of time. Can be fixed with a longer timeout. This also happens to me on Arch and yeah it’s kinda annoying.
Normally updates don’t change a thing on Linux since the system runs on RAM. However, with these systemd updates, things have changed. Without systemd, it’s still the same more or less.
Oh, I meant a running system. Usually you would only need to reboot if you want to use the new kernel right away after an update. For most of the programs, you don’t even need to restart them if they’re already running. However, if you restart them they will run as the newer updated version.