OWA 2013 SSO - Client initiated form Logout

Maybe, you don't lose anything in trying. :P

Anyway, if you want to do more troubleshooting. I create an iapp using the same version, the logout is done in the APM policy configuration. The URI used is "/owa/auth/logoff.aspx".

Try to access the exchange server directly, and log the HTTP requests with something like Fiddler. Then you can see what is the correct page to logout, and you can apply to your configuration.