Blizzard said in the Season Dev stream they said if you have more than 1 stack of Zoltun's Warding left you will get the regular reward chest, a minor Wardwoven Chest and a Rare Wardwoven Chest.
I took 21 stacks of warding from the statue because I'm crap at avoiding the traps and I...
A Wardwoven chest (the one with the icon above) is an extra reward for keeping at least one stack of Zoltun's Warding until completion of the Vault. Extra Loot!