Microsoft removed mandatory registry key check for Windows 10 last month, in March. The registry key was removed to prevent Windows updates from being installed on computers running antivirus software incompatible with the Meltdown and Spectre patches. Microsoft said in January that Windows computers that use a custom antivirus product that does not add the registry key (hence is compatible with the Spectre patches) would not receive any Windows security updates. This was a big issue because incompatible antivirus products would crash and BSOD Windows systems.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-removes-antivirus-registry-key-check-for-all-windows-versions/