Sealed Birth Certificate in Michigan

I am aware that Michigan is notorious for being very restrictive with their adoption records, but was wondering if anyone had any firsthand experience. My situation is a bit different, as I am not the adoptee. My grandmother was adopted around 1920 to a couple that was related by marriage to her family. Her birth certificate is over 100-years-old at this point, but the state will only release her birth certificate with her adoptive parents listed. I was told in Lansing to petition the court which finalized the adoption. I am not sure if it was finalized in Wayne or Oakland County, but am pretty sure it was finalized in Wayne. I spoke to someone at their adoption unit and they told me that they are unable to release the sealed birth certificate to direct descendants (though that's not what I was told originally). I find all of this to be ridiculous, as we know who her biological parents were, as did she. Aside from the fact that she knew who her biological parents were, those records are about 100-years-old. Everyone involved, including my grandmother, are deceased except for direct descendants. I do not understand why it is so difficult to get these records, especially the older ones. Another thing the person from the adoption unit mentioned to me is there was a law passed in 2010 that prohibits the release of information to anyone except for the parents or the adoptee, yet Section 710.68 states, "(20) A direct descendant of a deceased adult adoptee may request information under this section. All information to which an adult adoptee is entitled under this section shall be released to the adult adoptee's direct descendants if the adult adoptee is deceased." This is why something doesn't make sense in terms of trying to get her original birth certificate. Any direction is greatly appreciated.