Well, if it has got legendary power, so the item is definately new. I'll see If I have some in stash later and try to reforge some on my DH to cross check.
EDIT: just fast checked my season mail and some chars and I don't have this belt... I could have sworn that I got at least one. If I got some time tomorrow I'll maybe be lucky to upgrade one If I succedd I'll let you know.
Maybe It will be some kind of long shot, but is it possible that you have this belt for very long time as well as you DH and belt itself is legacy item? That's the first thought that come to my mind after reading your post. It is possible that legacy items could reforge in different way.