"...The document in full reads:
In order to provide the best customer experience, if a customer reports that their iPhone X is having Face ID issues, you may be able to resolve the issue with a rear camera repair. Run AST 2 on the customer's device to check the camera. If the diagnostics find issue with the camera, perform the repair to see if the issue is resolved. If the issue is not resolved, perform a whole unit replacement instead of a same-unit display repair.
Apple has not commented on this matter publicly, or launched any sort of official repair program, as these are internal guidelines.
Affected customers can book an appointment with an Apple Authorized Service Provider or Apple Store via the Contact Apple Support page: iPhone → Repairs & Physical Damage → The Topic is Not Listed → Bring In For Repair. Following those steps also presents options to contact Apple by phone or email...."