If you look closely at an X-ray transmission photo or a close-up photo of the motherboard, you can see 12 metal contacts on the circumference. Normally, the Ethernet signal line is 2x4, but I guess they made it 3x4 so that it is equivalent even if the connector is turned 180 degrees. On the other hand, I think the 15.9V9A DC current is supplied by the center electrode (positive) and the surrounding cylindrical electrodes (negative).

"Radiators" could be bass acoustic amplifiers using Helmholtz resonance, related to the two-speaker active cancellation used in recent Apple product speakers?