We have a mixture of two 2012 and three 2019 domain controllers in our environment.
We have a GPO for domain controllers that is set to download updates and schedule them for installation (and any reboots) for 4am on Saturday mornings. The 2012 DCs follow this GPO, but the 2019 DCs don't. They will install updates and reboot at random times.
I did a gpresult to make sure that the GPO was applied and the settings were correct. In looking at the registry of one of the 2019 DCs, all looks to be correct? Registry screen shot below: