[LyndsySimon]

Those things don't necessarily have to be mutually exclusive - though grant, they likely will be as implemented. Face ID is incredibly convenient on phones, and I while I didn't expect to care either way on the iPad, it's just as nice there. My only complaint with my 11" iPad Pro's Face ID is that the sensor is only on the "top", and is almost always covered by my hand when I'm holding it in landscape (which is pretty much always). A second sensor on the right side of the device, near the magnets for the Apple Pencil, would be very welcome.

For a laptop... I'm not sure exactly how that would best implemented. The easiest thing to do would likely be to hardwire an LED to the sensor so that it couldn't be activated without notifying the user. Otherwise... perhaps it could be implemented as a self-contained authentication device that sent some sort of hash of the user's facial features to the OS, instead of the actual image? I'm not familiar enough with how the technology works to say for sure.