Yeah it's the Animal Realm replacement.

Nagato can use his power to control their bodies via the chakra pins throughout their body. Nagato needed a "source" to do it from, thus God Realm. He's like the receiving tower for the chakra waves. Knock that tower down, and all of them will fall.

It would not surprise me, at all if they "capture or kill" God realm and these bodies, and Nagato uses J Mans body as his new God Realm....