That's not the experience I currently have with TouchID on my MBP. An authentication situation comes up, all I have to do is reach over and place my finger on the sensor ... there's no other physical interaction required on my part for that authentication. FaceID would be the same as it is on the phone, I imagine. Something that requires me authentication occurs, I see a very brief 'FaceID' style notification which goes away almost instantly, and the thing has been authenticated. No need for having to touch a key/keys to start a TouchID or FaceID process.