Are you looking for someone to blame if you don't make it
50 - 50, look at the post above your first post in this thread, the op hit the booking desk at 6pm and missed out.
J doesn't help secure a place on the tour.
J does help you get off the plane quicker, and to the tour desk quicker.

As said, the presence of this free tour has made its way onto Tripadvisor.
Good luck.