Not quite the same thing....
A timing belt is a wear item and a stock replacement part that the Ford shop has in stock, for the car.
ATX external filter??? The shop has never seen one of these and Ford doesn't specify one (FWIK) for the tour. A dealer service department is not going to customize your cars mechanical design for you, at least not willingly. They are just not in that business and only want to put parts on that Ford will pay for if it breaks or causes problems. They just can't stand behind some 3rd party part added to your ATX hydraulic system, but might do it if they can void any warranty on the car.
