I think that endpoint was for authorization_code flow apps. If you're password flow, when your user clicks log out in your app, you can simply clear user's session(access_token etc) on the client side and then request a new guest token and set to user's session so the user will then jump into guest experience.
(Little background here: for autorzation_code flow apps, while user logs out your app, you're logging our
your app, so he/she can be logged out of your app but still logged in with
delivery.com service, that way, when your users want to log back in, they don't have to type credentials to
delivery.com again.
This is a good reading.)
Hope this is helpful.