The problem you are not getting is when you say "backed by" you literally mean they have gold stored away, and they do not. You can not "back" a currency by something you do not own... sorry, but I'm afraid you are not understanding.
Who am I?
BORIS!
How do you mean they do not own?
Of course they do. The gold is from Nadir, one of the biggest raffinery of gold in the world (if not the biggest) and it is stored in Loomis (the biggest company in the world which stores gold). And if Xaurum holder wants to receive the gold in his/hers hand, he/she can get it. See the pictures :)