I have no issue with security devices requiring some sort of approval (which should be made available to self service), but devices like the screen, camera, battery, buttons, memory/storage, ports, speakers, etc, should be allowed whether or not they are factory.
Just FYI, iPhones don't have fingerprint sensors in the screen. Older models with fingerprint sensors have a capacitive sensor in a physical home button/capacitive pad.
Newer iPhone's exclusively use FaceID for biometrics, which uses the camera array at the top of the device.
Forget the sensors, they can say it's a security related since it can display private info and their fans would defend that. You can bet they would make some excuse for almost everything and fight for it in court.