When children are temporary court wards and a Supplemental P.C. is filed with the court and the parents voluntary release their rights is it necessary to set a Post-Termination Review Hearing?

When children are temporary court wards and a Supplemental P.C. is filed with the court and the parents voluntary release their rights is it necessary to set a Post-Termination Review Hearing?
Or are the children committed to the MCI/Michigan Children's Institute under the juvenile code?