Comment by Const-me

I did forget to mention something important. Since about Vista, Microsoft tends to replace or supplement C WinAPI with IUnknown based object-oriented ones. Note IUnknown doesn’t necessarily imply COM; for example, Direct3D is not COM: no IDispatch, IPC, registration or type libraries.

IUnknown-based ABIs exposing methods of objects without any symbols exported from DLLs. Virtual method tables are internal implementation details, not public symbols. By testing SDK-defined magic numbers like SDKVersion argument of D3D11CreateDevice factory function, the DLL implementing the factory function may create very different objects for programs built against different versions of Windows SDK.