Legally - Whose child is he?

My foster son has been in our home since birth. Our local DHR was not able to get TPR so we entered into a private open adoption with the birthparents. BPs voluntarily terminated about 2 months ago and our state only has a 10 day revocation period. Our petition has been filed and excepted by the court earlier this month. However, DFACs has insisted on staying involved until the adoption is finalized. They are insisting that the BPs who no longer have visits through the agency continue working on a case plan. My understanding is that legally our son is a "ward of the court" during the 60 day petition period. Admittedly, our county office has never had a situation like this before, but doesn't it seem like adding insult to injury to make them continue to work on a case plan for a child they have already terminated on? I would love some input and firing power to get them to back off. Thanks