Also new to DP and I was told that while backing it dumps the air so there is no downward force that could render the rear drive wheels useless. Think backing up over a curb and tag lifts rear duals off the ground.
Mine has a switch for manual and auto. I leave it in auto and when I select reverse it automatically dumps the air. When I select drive, the tag begins to air up again.
Tom and Gloria 2017 Newmar Ventana 4369, TOAD: 2015 GMC Canyon, Blue Ox Towbar, Baseplate and M&G Braking System