Microsoft has changed the Windows Update service for Business with Windows 10 version 2004. The company has removed the ability to defer manually Windows 10 feature updates using the Windows Update page in Settings.
Update less: Last year, we changed update installation policies for Windows 10 to only target devices running a feature update version that is nearing end of service. As a result, many devices are only updating once a year. To enable all devices to make the most of this policy change, and to prevent confusion, we have removed deferrals from the Windows Update settings Advanced Options page starting on Windows 10, version 2004.
So, with this change, it is no longer possible to manually defer updates for 365 days using the Windows Update settings Advanced Options page in Pro, Education and Enterprise edition of Windows 10.
Microsoft recommends using a Group Policy instead, as follows.
If you wish to continue leveraging deferrals, you can use local Group Policy (Computer Configuration > Administrative Templates > Windows Components > Windows Update > Windows Update for Business > Select when Preview builds and Feature Updates are received or Select when Quality Updates are received).
If the policy is not set, devices will be upgraded to the to 20H2 once users install May 2020 Update. Earlier, it was possible to postpone feature updates up to 365 days.