In the 1990's, as part of our club's activities, a small party of members visited a local British engineering manufacturer that was producing parts for major car companies and engine builders, Jaguar, Perkins etc. As we observed the finished products coming of the machines, king-pins, camshafts etc., these were being placed in containers marked, for example, Land Rover, then Quinton Hazell and lastly Del Boy's Car Parts (obviously, I am making that up but you get the idea). The components, whatever their destination may have been, were exactly the same, produced from the same material on the same machines and subject to exactly the same quality checks. This is one of the reasons I have never been troubled by the thought of buying 'generic' components for my Volvo's, indeed I actually demand that they are fitted because of the price differential.
This particular small British manufacturer no longer exists, it was taken over by an Italian firm and then closed down but I assume the same practices still obtain, just not in this country anymore.