My thing is say, someone like Phong who sells "high" end stuff. Manufacturing the individual parts based on Gen items should not be too hard. if built separately, to gen specs, then its just a matter of fitting/miking and trimming to achieve that perfect/water tight fit.
Maybe one factory can be better at main case and case back, while another one can produce a better bezel assembly, etc.. I know this opens up a huge ordeal with correct tolerances, etc... but
Just saying
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