Apple continues to complicate iPhone screen tech, not just because it perhaps has a monetary incentive to discourage third-party repairs, but also because it wants to trump Chinese suppliers who make alternative parts.
iPhone 13’s screen IC must also be transferred when replacing screen to make Face ID work
So, if you tried replacing an original iPhone X’s display with another iPhone X’s screen, the True Tone feature would stop working.
Chinese repairers were able to outsmart Apple by copying the data as the chip was readable, erasable & programmable. The code can even be transferred to a non-original display now.
Presumably to counter this, Apple added another memory chip to iPhone 11’s integrated circuit. The second chip is read only (ROM) and it cannot be copied to another display. So, if you replace an original iPhone 11’s screen with another genuine unit, the phone would detect that the code programmed by Apple isn’t there. As a result, True Tone would stop working and you would get a message that the screen is not original.
Although this could be a bug in iOS 15, the exercise has shown that the integrated circuit is getting more complicated with each generation.