I took a look at this, and I don't think it is possible to make it work.
The SSO login/logout process uses browser redirects/cookie mangling/etc so it cannot work when the user is logged out from the backend.
I checked and Moodle does not provide a way for admins to log out users like Joomla does, so there's nothing to hook to.
But for session duration, you can just same the same duration in Moodle right?
