I took my current Mustang to be service there twice for recalls this year and both times I've had issues with their service department. Because of that I took my order to Kelly Ford instead.
You're paying to have the ability to change the exhaust volume integrated into the car instead of having some jank 3d party solution to achieve the same effect. Aftermarket catback/axlebacks uses the factory actuators for the valves so it is not like you are losing any functionality if you want...