On idp signout, logout endpoint is not called

We are using 20.0.3 Keycloak as a development environment for our saml implementation
we are trying to simulate logout from idp, and doing so by manually Signing Out the user’s session from within the Keycloak admin ui.
We are expecting our post endpoint to be called/notified so that we can kill our local session/token.
However nothing is ever received.

I have configured both fields:
Logout Service POST Binding URL
Logout Service Redirect Binding URL

I have also played with the Front channel logout setting but on this latest version outcome is the same