It is very clearly described in the original post as well as someone else posting a video of it later on. It allows a person with legacy controls to run away from an enemy at full speed while still facing them the entire time. This (VERY) effectively keeps them from ever exposing their back/flank to the enemy which is reducing the effectiveness of certain classes and skills. While it can be accomplished by macros you would have to spam the macro 2-3 times a second so many people resort to 3rd party software to auto-fire their face target keybind in the background so they don't have to think about it.