We were driving from Death Valley to Las Vegas yesterday, saw these chargers on the map and chose to use the Alta Dr. 150kW, both unoccupied. The picture above shows a black Model S plugged into the first charger. My wife backed up to the second charger, the wheels contacted the black and white parking guard and the supercharger cord would not reach our charge port! We parked our car at a right angle so the cord would reach. This blocked the narrow driveway and both chargers for the 17 minutes we were there, but fortunately no one else came by.
It did not occur to us to try the first charger when the second one had the defective parking design. But users should take note that only one charger is usable at a time until someone moves that second parking guard farther back.