That’s exactly the point to this proposal. They can’t remember or function at all, so let them make their wishes clear before their decline.
That would be fine but by the time a dementia patient is diagnosed they are already in decline.
In decline, yes, but often/usually still coherent. It is the last chance they have to express their true wishes before cognitive decline makes that impossible.
Reg, how do you measure cognitive decline?
I have no idea. I assume specialists in that area have methods, but I don’t know what they are. I don’t care, either. To me, each of us should get to decide for ourselves when the decline is too great.