CanBus is CanBus, right? Only on paper.
So what is the difference? We made this easy. In one picture.
In the above pic, you see all the accessory lighting items that Honda offers for the 2018+ Goldwing circled in red. Now we have taken out anything that Honda added a specific circuit or connector for; 3rd brake light, puddle lights, and fog lights. By the way, you should see nothing circled in red and that is on purpose. Honda does not offer any lighting products.
The items circled in yellow in the pic shows all the accessory lighting items that Harley offers for the Ultras. All of these connect into the factory wiring for the rear lighting. They are NOT connecting into specific circuits. They all piggyback into the main harness.
Ok. So why should you care? This visual shows us that Honda did not create any extra allowance into the CanBus system to power extra lighting. Harley did. By designing lighting products that plugin as they do, Harley made sure that the rear lighting was robust enough to power all those extras. And has protection measures built into the BCM (body control module) that runs the lighting.
Plug & play safely, friends.