BuddyPress.org

Yep that’s exactly correct. In theory, to create a post from within the Group forum, you should not need cookie integration, because the XMLRPC request happens very ajax-like behind the scenes and does not require for you as a specific user to be logged into both platforms.

However, to click over to the forums and post inside of them, you will want to have cookie integration for the transparent optimal user experience that most of us are striving for.