I agree....I'm using the T56 switch. You don't need a relay for it. I don't understand why you'd need to go through the ECM either. Why would the engine need to know when you're in reverse?If the wires go through the ECM, I'd put them on a relay.
The T56 has a reverse switch on it, you don't need to go through the ECM. And maybe yours is that way, but just bundled into the harness.