I also thought once you have registered it would be a different way to leave but apparently it's not happening yet.
In addition everything I saw on line involved using the device to enter your info rather than waiting in line then wait until it's your turn to go through the passport process but the devices were not in use when I arrived/departed.
You check in first and they'll tell you what gate to go to and then you end up doing the same thing as you did upon arrival and hope there isn't a long line.
You may have to adjust the time you get to the airport especially if it's late morning and afterward.
I agree the time of day you arrive/depart could make a difference.