Not sure what that is or what menu it is. But yeah, the updates are not automatic, you have to manually start it. That "must restart after the update" thing is related to systemd, not openSUSE.

I don't think it's systemd's fault that I repeatedly experienced general system unstability after installing updates with zypper.
By this I mean several elements of the system becoming unresponsive, like the shutdown, reboot, log out buttons stopping from working (them being pressed only resulting in a syslog error about being unable to start the program that shows the countdown), but also other programs like firefox acting weiry.
I don't think it's the fault of opensuse specifically.

And if you think about it, it's logical that this would happen.
Because version A of programs is what is still running, but the filesystem now has version B of a lot of things including executables and libraries, with lots of changes, and the assumptions for which version A programs were coded do not hold up anymore. And they crash, not even start, or do bad things. Processes that make use of D-Bus are especially sensisensitive to this, but others like firefox sometimes get tangled into it when they load a library only after the files were updated (yes I've experienced that too, both on linux and windows).

It's no wonder windows installers always ask you to close all (related) programs before installing or updating. It's not unique to windows: android kills the app when it is updated, abd system updates require a restart as well. I don't know what does flatpak do, but I'm sure that after updating the package, only after restarting its app will the changes get applied.