Legendary Upgrade issue

When I upgrade my Legendaries (which I have done 3 now) the secondary stats nor the equip bonus change. The only thing that changes is the ilvl. When I make a new Legendary, the stats are higher than lower ilvl legendaries and they have a socket. Is this a bug? Or did blizzard purposefully make it that the only thing that changes on an actual upgrade is the ilvl?

For instance, my DH Havoc cloak went from 235ilvl to 262ilvl but the secondary stats stay exactly the same between the 2 and no socket was addeed and the equip bonus did not change. Same thing happened to my DH Veng gloves. Also my BM Hunter boots. When I crafted a new ring for my Pally it got a socket and the stats were significantly higher and that was a 249ilvl item.