I recently had to swap the headphone/proximity sensor/face ID illuminator assembly on an iPhone X. The illuminator is cryptographically coupled to the phone, so you loose face ID when swapping in a new part.

I understand why Apple would secure the fingerprint sensor, the dot projector and the depth camera, but I fail to understand why Apple did that with the illuminator. It doesn't seem relevant for security? Anyone got an idea besides "lol fuck consumer repairs"?