I think that is the function that’s being used.
I had a quick look through the WordPress code and am not seeing an obvious way of getting this to work. If this is not an action that you are performing very often, Discourse admins can log users out of Discourse by clicking the “Logout” button that’s displayed near the top of the user’s admin page. To force users to log back in via SSO, you could manually log the user out of Discourse, and then log them out of WordPress.