Does PMAC costing work in multi org situation?

We are trying to implement PMAC costing. We have multiple inventory organizations. We want to keep one cost org and have the inv orgs under that. Going through the implementation guide, it seems Cost Organization Association can be leveraged. So, we setup a cost org and did the org associations, and ran through some transactions. But, system is not doing PMAC. Here are the details -

Defined a cost warehouse association between

OR1 (Parent) and OR2 (Child) orgs.

Did a Average Cost Adjustment for item TEST-1000 in OR1 (Parent), quantity 100, Cost $2.00, period - Sep 2017

Received a PO in child org OR2, quantity 200, $10, period - Sep 2017