Windows Hello can't be fooled by your identical twin

[PuremasterZ]

So what if someone used a mask of our face?

[Corky34]

Is Windows Hello a bit like the Kinect always on thing, to be able to login via face recognition wouldn't the camera have to be permanently switch on?
In the Microsoft FAQ on cameras and privacy it says...

Do I have to have my camera setting turned on to use Windows Hello?

No, if you choose to turn on Windows Hello, it will use your camera to sign you in even if your camera setting is turned off. If Windows Hello is turned off, it can’t access your camera.

(Windows Hello, part of Windows 10, is a new way to sign in to your devices, apps, online services, and networks.)

If you turn off your camera shouldn't that mean you can't use Windows Hello, shouldn't turning of your camera mean nothing can use it?

[TheAnimus]

No you turn your camera off to save power consumption. It will be 'woken' by Hello, then slept again.

[Corky34]

It can't turned off when Hello is enabled, otherwise how would it know you just sat down in front of it, going on this reddit post if Windows Hello is enabled your camera is permanently switched on, even if the webcam privacy setting is set to off.

It seems that setting only effects Modern apps (aka Windows store apps) as going on the FAQ both Windows Hello and Classic apps (aka anything that isn't a Windows Store app) bypasses that setting, I just assumed that the "let apps use my webcam" setting would apply system wide and not just to Modern apps, in other words, that off actually meant off.