RNS-E and heated mirrors doubts.

So, I think we must conclude that the user manual is wrong and the only form to start the heated mirrors is pressing the rear demister button.
Over the last few weeks, we've had some cold weather in the Lake District area, so I've been able to test the on/off logic of the heated mirrors. Surely enough, it is as we all thought; the heated mirrors switch on/off with the rear screen demister. The user manual is chatting nonsense.