No. I already have the MyDisneyExperience app loaded and ready to go with the AT AT picture visible on my screen (see post 1).
At 6:59 or 12:59 I go back from the MDE app to the home screen of my phone.
I watch the second hand and when it hits about 10 seconds before the hour I start tapping my foot to the seconds and go back to the MDE app.
I then watch the clock at the top of my screen and as soon as it flips to either 7AM or 1PM I click Join then. If I click even a second early (on my phone) I will be too early and most likely lock myself out of a BG.
I think it's best for you to check out the
Boarding Groups: Rise of the Resistance *No Spoiler* thread. Post 1 will explain things again. That entire thread is dedicated to people obtaining BGs for the ride.