I agree with you that every parts must be substituted with genuine parts in case of component damage. I had tried to replace s6 battery and spent like $500 but alas I failed. After 4-5 month the battery gets swollen and the backcover gets damaged costing me more. So I had to dump it and I am never going to buy any Samsung shits.
I got k20 pro and I hope I can get genuine battery for it after few years.
Further such things prevents theft which is a huge problem imo. I think apple should provide user to switch these display but it should warn that the part is genuine or not, just in case.