[theranger]

It would not be a safety issue indeed only until the replacement part includes some mitm hardware that tampers the face id authentication flow. And this can be planted into the genuine looking replacement part as well.

[josephcsible]

I expect that at least one of these things would have to be true:

1. The MITM hardware could be installed into the screen that's already paired with the iPhone, so the serial check wouldn't help

2. The MITM hardware would make the screen look non-genuine regardless of serial, so the serial check wouldn't be needed