I ended up with an orphaned WH-00025. It had the big connector on one and and a Molex, ostensibly for the disconnect switch, on the other. I had just spliced the disconnect switch onto the other Autopilot harness, so assumed the WH-00025 was not needed for my installation. I have performed a casual test of the autopilot at this point and everything worked as expected, so I suspect that I was fine with not using the extra harness.