True, but it works in the factory wiring because the total current drawn by the headlights passes thru the switch. The purpose of the relay conversion is to remove that high current from both the switch and the bulkhead connector. As such the headlight switch only passes the minimal current required to close the relays.
Thanks for that verification. I first heard of the GM switches having an internal circuit breaker back in the later '70s when some desired to install aircraft landing lights in place of their existing high beam lamps. Too much juice, so the circuit breaker shut things down.
As for external circuit breakers, the middle '80s GM pickups with power windows use a circuit breaker that plugs in as a normal plug-in fuse might plug in. Male blade terminals, which would be easy to wire into an existing relay-controlled headlight wiring. One for each side? Seems like they were either 30A or 50A? Cad-colored metal, with the amp rating stamped into the narrow top length dimension, along with an appropriate color code stripe.
In the case of external driving lights, some would wire the additional "super high beam" lamps such that they could switch between them with the existing dimmer switch. Of course, the additional lamps would be relay-controlled due to their higher amp draw/additional wattage.