IDirect3DSurface9Ex Does not Exist

On this page https://docs.microsoft.com/en-us/dotnet/api/system.windows.interop.d3dimage.setbackbuffer?view=netframework-4.8 which appears to be https://github.com/dotnet/dotnet-api-docs/blob/master/xml/System.Windows.Interop/D3DImage.xml, it states the IDirect3DSurface9Ex must be used for multisampling. However, no documentation about IDirect3DSurface9Ex exists, and the D3DResourceType enum only contains 1 entry which is IDirect3DSurface9. Is this a mistake in the Wiki or the code base, and how would one allow multisampling on a D3DImage then?