Ubuntu – Kubuntu Energy Saving event on power button pressed not working

My Aspire 1810TZ is running Kubuntu 13.10 on an encrypted drive. I have enabled hibernation in file

/etc/polkit-1/localauthority/50-local.d/com.ubuntu.enable-hibernate.pkla

[Re-enable hibernate by default in upower]
Identity=unix-user:*
Action=org.freedesktop.upower.hibernate
ResultActive=yes

[Re-enable hibernate by default in logind]
Identity=unix-user:*
Action=org.freedesktop.login1.hibernate
ResultActive=yes

I CAN hibernate and resume with
sudo pm-hibernate
and by using the application launcher ( "Leave – Hibernate" )

I set "Energy Saving – Button Events Handling" to "Sleep when laptop lid closed" and to "Hibernate when power button pressed" (for AC power, battery and low battery mode each). Sleep mode works fine.

When I press the power button the system shuts down / hibernates. But when switching it on again it just boots normally and has to start the open applications again.

So my question: What is the difference between the event "when power button pressed" and sudo pm-hibernate?