OpenGL no more 'wraps WinAPI functions' than any other program or library that happens to run on Windows. OpenGL is platform agnostic, the need for Windows API with OpenGL apps is to get access to the driver frontend, and ( perhaps ) obtain a window / device context, although OpenGL itself mandates no windowing method specifically. Maybe the software reference implementation that ships with windows wraps WinAPI calls, but that's not the version of OpenGL that most gamerz see ( install graphics card drivers and you get the driver manufacturers accelerated OpenGL driver, which should go as direct-to-the-card as possible. I have no idea what they put in their drivers, but I'll bet they make as little use of the Windows API as they can get away with ).

Same with DirectX, it is supposed to go 'under' the API, as in, provide as close-to-the-metal access to the graphics card as is feasible, card vendors provide the implementation, and if this uses WinAPI in any way, thats secondary to using the features of the hardware.