I think you will possibly find that the person who made the video is wrong in their assumption about the LCD and FaceID. Depending on the application, LCD screens can use what is know as EDID, which I believe has been replaced with DisplayID:
EDID -
https://en.wikipedia.org/wiki/Extended_Display_Identification_Data
DisplayID -
https://en.wikipedia.org/wiki/DisplayID
This is data which is sent to the hardware logic of the device which gives it various information about the screen. Things like manufacturer, screen size, serial number and others. Not every LCD screen on the planet uses EDID or DisplayID but as I said, it depends on the application.
Now for those who do board level repairs, on the LCD connection on the logic board there are two data signals commonly refered to as IC2_SCL and IC2_SDA, meaning IC2 Serial Clock and IC2 Serial Data. These two data signals provide serial communication from the LCD and the iphones logic board and visa versa. Information from the LCD will be sent to and from those data signals. Now if Apple are using EDID or DisplayID, each LCD will be encoded with it's own unique set of information which upon first power on of the phone will be recorded by the iphones logic board. LCD's that use EDID or DisplayID can be calibrated for optimum apperance.
The method is a bit similar to how Microsoft Windows encodes it product key with that of the machines hardware which when you replace some of the machines hardware, it requires you to re-register the OS. Apple are in my opinion doing similar with it's LCD, it's uniqure idenfitiers are encoded to that of the iphones hardware thus when you replace some of the hardware, in this case the screen, various things stop working properly, therefore in a way you having to re-register the new screen with the iphones hardware. That is in my opinion how it is working.
I've not seen the hardware on an iphone 13 screen but I bet there is some tiny amount of electronics on it which holds the information about the screen. If you've ever watched videos of Chinese screen refurbishers, you will notice they desolder a flex cable off the broken LCD and resolder it onto the new LCD. Many times you will notice when in use, the screen appears darker and thats because the old broken screens calibration data is still inside the electronics that is on the flext cable, hence why is needs to be recalibrated for optimum apperance.
This could be why in my opinion changing iphone 13 screens from one iphone to another stops the FaceID from working because the data being sent from the LCD does not match what is in the iphones logic board thus as a security measure, it stops FaceID from working, because lets face it, people from all walks of life use an iphone if the iphone is being used by a person who's job requires them to have security measures (security professionals, politicians, lawyers, bankers, designers, researchers, to name a few), these people would want to know that the information inside their phone is secure if their iphone was every to be stolen (it does happen). If all it took the thief to do is to remove the original screen and replace it with another and for the iphone to accept the new screen and allow FaceID to be set up, just exactly how is that meant to be a security feature?
For example, an Intel researcher uses an iphone 13 which was issued to them through work, basically a works phone. That iphone contains $ millions worth of engineering data and other information and as per company security policy, is protected by FaceID. Now a few day's later, that Intel researcher has their iphone 13 stolen, the thief knowing what they have stolen (it was a targeted theft). The thief tries the phone and notices it is locked with FaceID. The thief gets hold of a replacement lcd thinking they can bypass the FaceID security by replacing the screen and setting it up so it works with their face. They replace the screen and low and behold, the iphone says FaceID is disabled, the thief is unable to use the replacement screen to fool the iphone into setting up FaceID to work with their face, result, they cannot get into the phone, the Intel researchers data is safe.
Is this how screen changing and FaceID should work? People need to look at the bigger picture here. Not everything is about 'me' and how it might inconvience 'me' if they change a broken screen and FaceID stops working.
