Something like this, I imagine:

"The screen is bonded directly to the front-facing camera, so the screen assembly must never be separated in order to prevent tampering with FaceID. As an additional anti-tamper measure, we've also recently begun permanently soldering the harness responsible for connecting the screen assembly and TPM. Unfortunately, this means that the screen assembly and motherboard cannot be separated without compromising system security. For the protection of our users, we at Apple cannot in good conscience offer any individual parts other than the case and master screen+motherboard assembly."