As far as i know , the log out page is not available in the September release, it is available only from the november release,
It is a new feature in the the November release.
SAML single logout
With SAML single sign-on (SSO), you only have to log in once to access several web sites. There is then a potential risk that one or more sessions are not properly closed. By using SAML single logout you eliminate that risk.
Please find the link attached too.
Hope it helps.