Yes, it is, but there are a couple of workarounds. You can sync logout between Discourse and WordPress by adding a URL like this to the Discourse logout_redirect setting:
http://my-wp-blog.com/?request=logout
The easiest way to get users logged in on WordPress when they visit the site from Discourse is to link to the site on Discourse with an SSO link. You can get the form of the URL by inspecting the ‘Login With Discourse’ link on your WordPress login page. It should look something like this:
<a href="http://wordpress.dev/?discourse_sso=1&redirect_to=http://wordpress.dev/">Log in with Discourse</a>
Change the value of the redirect_to parameter to get users to a specific page.
A Discourse plugin could probably be developed that would automatically sync login with WordPress. It’s not something that can be accomplished through the WP Discourse plugin.