The wires going into the switch carry a digital signal, they do not literally, directly 'switch' anything. What happens when that signal is received by the computer is where the magic happens. Same is true at the other end with the lights...while there's power going into the module, it doesn't directly cause the light(s) to turn on...there's circuitry there that makes it happen.
I haven't taken the i3's panel apart, but have on my GT, which uses similar logic. In the rear panel, there are running, reversing, turning, braking, and fog lights along with license plate lights. TO control each like in the old days would require heavy(ier) wires, and 4-5 wires on each side. There's less than that, and most of them are smaller gauge. So, there's essentially one power lead, one ground lead, and signal wires that tell the panel which light(s) to turn on.
I think the only exception may be the brake lights which can work without the computer logic.
2011 535i x-drive GT, 2014 i3 BEV