According to Fujifilm’s original GX617 sales brochure, the six contacts are there for redundancy, not extra electronic features.

The lens/body connection uses six electrical contacts arranged as two banks of three. The brochure states that if one bank fails, the other bank automatically operates instead, improving reliability.

So the extra contacts are not for metering or advanced electronic communication. They exist to provide a more dependable electrical connection for the body’s electromagnetic shutter release system. That makes sense on a camera like the GX617, where dependable shutter firing is critical even though the camera itself is largely mechanical.