I got curios enough that I contacted Highlandridge. This is what he had to say.
The reason why on a 5.5 box you can turn 90 degree's is due to the fact our front cap has indents in it so the cab of the truck won't hit the front cap. Also the pin box is slightly extended by 2 inches to allow for more clearance. We don't use a slider or sidewinder pin box.
He also said the pin box is a---Lippert King Combo
2008 Cruiser CF26RK
2013 Ford Eco-Boost
Heavy duty payload - Max tow