I actually have had this problem for years, so it is not necessarily related to the latest opensuse but somehow this never gets resolved. In the past months I installed leap 42.2 freshly on several desktops and vm's and they all exhibit this same behavior: when you shutdown, logout or reboot, there is a delay of 5 seconds before the procedure executes. In the case of shutdown, the funny thing is the shutdown is immediate if you type it in a terminal, so I guess it must be something KDE related. I have not tried opensuse Gnome.

At one time, I thought it was a systemd timeout configuration concerning inhibitors, see your list:
sudo systemd-inhibit --list

there is even a nice kde system module to view the configuration:

but unfortunately this "InhibitDelayMaxSec" does not seem to change anything and wouldn't delay the logout, I guess.

Assuming everyone else must be having this delay too, does anyone have any idea where this delay is coming from? On a fast pc especially, this is driving me nuts