I suspect this is actually something to do with the fact that the Face ID sensors are projecting unique patterns across different devices. From the Apple Platfo

I suspect this is actually something to do with the fact that the Face ID sensors are projecting unique patterns across different devices. From the Apple Platform Security document: > After the TrueDepth camera confirms the presence of an attentive face, it projects and reads thousands of infrared dots to form a depth map of the face along with a 2D infrared image. This data is used to create a sequence of 2D images and depth maps which are digitally signed and sent to the Secure Enclave. To counter both digital and physical spoofs, the TrueDepth camera randomises the sequence of 2D images and depth map captures and projects a device-specific random pattern. A portion of the Secure Neural Engine — protected within the Secure Enclave — transforms this data into a mathematical representation and compares that representation with the enrolled facial data. This enrolled facial data is itself a mathematical representation of the user’s face captured across a variety of poses. https://support.apple.com/en-gb/guide/security/sec067eb0c9e/1/web/1 https://support.apple.com/en-gb/guide/security/sec067eb0c9e/...