That really seems to be just a reproduction of bits of the manual, but with added illustrations.
The manual doesn't expressly say it's not possible (or if it does, I haven't found it yet). In fact, it implies it is possible, because it doesn't list any specific exceptions to the instructions for turning it off.
It's only when you try to do it that you find it doesn't seem possible.
It was one of the first things I wanted to do - and the first thing I couldn't.
I know auto mode is supposed to mean you don't have to adjust the settings yourself. But it seems a bit literal if you can't even turn off face-recognition. It might well be useful to have the camera decide aperture and shutter for you. But it's not useful to have it decide what's a face and what's not - especially when it gets it wrong.
I can't believe there's no way to tell it not to bother.