From what information I got from D-Link, this is a new feature and is still being tested by FB.
There will be a FW upgrade that will need to be done with the 865L. This is a DIR-865L only feature not seen on any other model router.
Keep checking the main web site for FW update information regarding FB WiFi.
If you need more information beyond this, please phone contact your regional D-Link support office and ask for help and information.
Thank you.