This should be an violation of probate law.
When a person dies, there is a very short amount of time for any creditors to make claims on a persons estate.
After that time, the distribution of the assets of the estate are final.
I do not see how the IRS can retroactively attach the assets of a fully probated estate so what they are doing should be illegal.
I wonder if it was fully probated? My lawyer told me that many times no one wants to probate and estate, and sometimes houses just sit and deteriorate and fall down.
He had a client who contacted Medicaid and asked them if they would take the lead, because no one in the family wanted to. Medicaid said no, that they would not file their claim until after a claim was filed with probate.
Also, their are some people who quietly transferred the ownership of their home to their children years before they went on Medicaid, so that it would not be an asset in their estate. A real estate agent had my Grandma do this when she sold the farm and bought a little house in town, just in case.
At one time there were lawyers that went around writing trusts to help people avoid their homes being pulled into the estate for settlement of Medicaid and other creditors. However laws were written to make that illegel IIRC.