Got it. Didn’t follow your initial post. This wiring diagram may help as all the brake circuit is looking for is resistance carrying a very small current. Traditional folks have wired in a “fooler” or a brake magnet into the circuit that would normally feed trailer brakes. The magnets are readily available and cheap. I have not tried it on the newest Ford trucks, but it has worked in the past. All it takes is a single magnet.
No guarantee, but you are correct. This is a really common issue with Ford owners and I think an example of engineer overdesign! 🙂
Steve and Andra
2012 F350 6.2 gasser SRW LB
Fab Fours front and rear in case we run into a rhino
2019 Northstar Laredo SC