Apple has long discouraged unofficial service centers, where you can get your smartphone or tablet repaired much cheaper than at official outlets. That's why with the release of the new iPhone 13 line, the company has put a piggyback on users.
The author of YouTube channel Phone Repair Guru took apart the iPhone 13 and found out that replacing the display at unauthorized service center will cause Face ID facial recognition sensor to stop working. Although the screen and TrueDepth camera are separate components and they change independently each other.
For example, when replacing the microphone, light sensors and proximity sensors there is no problem , but when replacing the display there is a message that it not original, as a result Face ID stops working.
According to the author of the video, this is apparently a software protection mechanism provided by Apple. Apparently it recognizes original components by serial numbers and otherwise blocks Face ID. And there's nothing surprising about this: for example, in last year's iPhone 12, the camera started malfunctioning after being replaced in the absence of authorization.
As for the current case, there are workarounds, but they are too complicated, so most repair shops are unlikely to go for them.
Source: Phone Repair Guru