Makes sense.... if the controller was plumbed in after the ABS unit. If the unit was plumbed in between the master cylinder and the ABS unit, I would think that the controller wouldn't know the difference.If I understand keerucktly, Modern ABS put the Kaibosh on those.
On my brother's newer GC Overland, it has a modern gadget plumbed into the brake lines (came that way from the factory) that sends a proportional signal for trailer brakes.
I have one of those old style controllers laying around as well... it's just a hydraulicly actuated rheostat. The one I have is BIG and would be a bitch a to find a place to mount it in the cab.