Logout endpoint on Customer Account API not logging out user

Currently I am spiking out using the Customer Account API for user authentication with a view to implementing this on our headless app. I have managed to create a headless test app to log the user in, retrieve the access token and retrieve the user information. However logging out the user doesn’t appear to actually log them out.

To be specific the app redirects to the authorisation page (Customer Account API reference) and upon successfully entering email & login code the callback is called with the code which is then used to obtain the access token (Customer Account API reference) which is then stored in cookie along with the id_token that is also returned. I then use the id_token to logout the user with the logout endpoint (Customer Account API reference) which appears to succeed and so my app deletes the cookies. But when the process is repeated and the app invokes authorization again, the page doesn’t ask for the email address. Instead it directly calls the callback with the tokens which suggests to me the user is still logged in.

Why is the user still logged in ?