A recent analysis of Apple's Lightning USB cable shows that the pins on the plug aren't arranged symmetrically, suggesting that the Lightning port can dynamically reassign signals to each pin on the fly. "Dynamic assignment of the pins is the only way for the USB data to be routed" over the cable, according to boutique cable maker Double Helix Cables.
While the standard USB power is routed symmetrically, so that it always aligns with the same pin on the Lightning connector, the data pins are not.
"Take top pin 2 for example," Double Helix's Peter Bradstock told AppleInsider. "It is contiguous, electrically, with bottom pin 2. So, as the plug is inserted into the iPhone, if you have the cable in one way, pin 2 would go into the left side of the jack, flip it the other way and the same pair of pins is going to match up with the other side of the jack (as the electrical contacts in the iPhone's jacks are along the bottom)."