Adding to what Mark as stated, from my experience OE assembly line parts usually are within a tighter spec range. From my world tires, rotors, and pads. I've often said the best tires you'll ever have are the ones that came on your vehicle.
When I was tasked to perform certified FMVSS stopping distance tests I had to contact the tire, rotor, and caliper manufacturers and get a pallet of assembly line spec'd parts. All of the people I ever ordered from took the orders like I was getting a hamburger from McD. With our relationship with Kelsey-Hayes, we knew rotors within Ford's spec but out of the tighter assembly line range went into the Ford service parts boxes. For a period of time, the Midas automotive organization was part of our overall company. They would get rotors and drums directly from K-H, and when we had some of those parts in house for a training seminar you could see where the K-H and Ford insignias were removed or hidden. The next time I talked with a K-H engineer I asked him about it and was told the way out of spec parts hit the aftermarket.
I'd be a little suspect that parts in a Ford box no matter the suffix would be out of spec, but then I've got this Motorcraft motor sitting in my garage ........