Should softhyphen U+00AD be empty?

As I understand it from the Microsoft Character design standards, the softhyphen (U+00AD) is normally hidden, until it’s needed. I thought maybe the softhyphen is supposed to be an empty width=0 glyph? Just want to confirm whether that’s true or not? i.e. should it just ideally be double encoded with the hyphen or use a component of the hyphen?

I found contradicting statements. But it might not matter. It seems that the layout engine should not use the glyph anyway.