I thought the statue was a vessel of the juubis chakra because the manga stated the sage created the moon with chibaku tensei and put its body in there. Like Nagato did when he attempted to capture Naruto.
You are right. That IS true. But the statue is now in that cave. And Nagato was able to summon it chained up with a covering over its eye.
The only possibility is that someone summoned the Gedu statue there, and brought Madara to it.... BUT WHO? LOL. It would have to be a whole new previously not mentioned character... there is noone left.