RP-initiated logout can be used with any of the postMessage, Front-Channel, or Back-Channel logout methods but the current description makes it seem like it is only part of the postMessage method. The description of RP-initiated logout in the Session Management spec needs to be refactored so that it is clearly independent of the postMessage functionality.
For instance, the metadata values at https://openid.net/specs/openid-connect-session-1_0.html#OPMetadata are mixed together. The
end_session_endpoint metadata should be moved into the RP-initiated logout section.