Correct. Do not click “My Status” until right after BGs open (which lately has been 7:00:00am). That said, if the “Join Boarding Group” button is orange, that means it is active and go ahead and press it. Pressing “My Status” refreshes from the server so on the following page the “Join Boarding Group” button (in this case dark blue outline) will be active as long as it is after the issuance window is open.
See this post for step by step instructions with screenshots (specific to Disneyland app, but same process for WDW).