When an administrator sets the Turn off AutoPlay policy in Group Policy, a user can still access the AutoPlay settings in Control Panel and in the Settings app. This behavior is unexpected. Typically, users are locked out of the UI if a policy is controlling the corresponding setting.
This behavior is by design. The Turn off AutoPlay policy takes precedence over any settings change that are made in the AutoPlay UI.
This behavior is standard in Windows 7 and later versions of Windows.