That hasn't been the case, then, because I clearly remember OpenGL being translates to DirectX in XP/Vista days. Whether it was because anything >1.1 called that up or because the driver vendors chose translation over native, I don't know.
Original link seems to be dead but Slashdot references Vista layering OpenGL on top of Direct3D:
That comment references something else entirely - namely the Aero rendering system of the OS. This didn't affect applications that didn't use the Aero glass scheme (it was an option during window creation), however, or apps running in full-screen mode.
The Aero glass scheme was hardware accelerated and only worked with Direct3D, thus any OGL context created for a window using this renderer would have to run via Direct3D.
This is a very special case and as noted earlier, easily circumvented by simply not using this feature in your app.
Original link seems to be dead but Slashdot references Vista layering OpenGL on top of Direct3D:
https://slashdot.org/story/05/08/06/177251/windows-vista-may...