I guess I see it differently (though I really don't care whether FaceID is or isn't implemented on the laptop). iPad Pro when docked to the Apple Magic Keyboard, which is how my iPad Pro is often used, is pretty much how I envision FaceID on laptop would work:
- when notification wakes up iPad, if you have setup notification such that no previews are granted unless FaceID is positive, then you'll need to FaceID in to see preview. This requires no touch input because when notifications appear, it wakes up the iPad but doesn't log you in unless you're authorized via FaceID.
- when iPad is asleep, you either touch screen or tap keyboard to wake it up and automatically FaceID will detect whether you're an authorized user.
- when iPad is "closed" (i.e., Apple keyboard is closed), then when you open the keyboard, it will wake up the iPad and it will also use FaceID (without further interaction) to detect if you are an authorized user
I think this is how FaceID on a laptop, if implemented, would pretty much work like.