Comment # 11 on bug 1077633 from Fabian Vogt

(In reply to Ludwig Nussel from comment #10)
> This is only half done. The dialog apparently just disappears now. The part
> where the applet should tell to relogin, reboot etc is still missing.

It's not missing - it's not needed.
The update says:

plasma-pk-updates: RESTART "application" is required for package
"openSUSE-2017-1228;1;noarch;repo-update"

Which means PackageKit::Transaction::RestartApplication.
Relogin is only requested for PackageKit::Transaction::RestartSession and
reboot only for PackageKit::Transaction::RestartSystem.

So not prompting for a relogin is correct.