I'll bet there's some creative board layout so that the relevant controller IC and supporting passives can be soldered onto the back of one of the 5, then have solder jumpers or some such to actually connect it into the circuit. That way, you're not adding miles of unused trace to an active bus.

Of course, having a 5x PCB fab, but 4x+1 assembly would probably double the cost for a single turn of the device.

I would love to hear more about the process of making 5-fold symmetry work for board layout. That sounds maddening to get right.