Microsoft has started training their machine learning algorithms by automatically updating Windows 10 2004 devices to Windows 10 21H1, the May 2021 feature update. Microsoft states that they are throttling availability for this update over the upcoming weeks, and it may not be available to all users. The new feature update is also available for deployment using the Media Creation Tool or via WSUS. The May 2021 Update is an optional update displayed when users manually perform a ‘Check for updates’ in Windows Update. Microsoft says they are using machine learning to improve the reliability of the Windows Update experience.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-starts-autoupdating-windows-10-2004-to-windows-10-21h1/