This article really should have been titled “Apple hobbles major security feature of iPhone 13”
Pairing the forward facing camera assembly to the phone prevents the module from being swapped out with another unit that can inject images into their authentication pipeline. It’s actually a cheap and relatively simple attack to bypass the facial authentication for anyone who has physical access to the phone. It’s actually quite concerning that Apple backtracked on this.
The front facing camera and Face ID components
are not a part of the display assembly.
The display assembly just has cutouts in the back layer allowing the cameras, lights and sensors to see through it. To them, it's a flat sheet of glass, and nothing more. The camera assembly is connected directly to the Logic Board; the display isn't a middleman in the electrical chain of power, let alone communication.
The issue people had with this limitation isn't that replacing the display would disable Face ID - it's that replacing one component would have an effect on another, completely unrelated component's functionality.
I can't see a reasonable instance where the IC on the display is part of the authentication chain either. It would make absolutely no sense to pipe that data from the cameras and sensors onto the board, back out to the display, and then back onto the board again, especially given how this functionality is supposed to be baked into the SoC (A15). What I do suspect is that the IC on the display contains EDID information, serial numbers and perhaps calibration parameters, and that serial number not matching what's in the SoC's internal records is what disabled Face ID.
If you’re laughing and saying an iPhone 6s doesn’t take 5 hours to fix, try doing it.
A display replacement on a 6s? Even transferring over the cameras, Touch ID button, front facing speaker, backing plate and reapplying the adhesive around the border, I was in and out in about 45 minutes. Granted it wasn't my first rodeo with a screwdriver by any means, but I'm no experienced phone technician either.
4 to 5 hours is extremely unrealistic for that repair. Not even replacing the entire rear housing, transferring the Logic Board, Camera and other components took that long.