I do not know but I suspect that WINE's various Direct3D code utilizes OpenGL nVidia Extension or higher level OpenGL ARB Extension rather that lower one.
That's why while INTEL OpenGL driver does support DirectX7, DirectX8 level 3D wine does not able to run many games on INTEL Linux graphics driver. While those many games run on nVidia Linux driver.
I hope WINE will someday have better INTEL OpenGL support.
Wine is doing nothing wrong we use generic OpenGL extensions all through Wine. The issue is that the intel drivers don't offer all opengl extensions we need for decent d3d9 support, if the gl support isn't there we can't support it. Second the quality of the intel drivers still isn't very good, sure recent versions support GLSL, FBOs and other things but the drivers are first of all buggy and second very slow for those purposes. Further ATI works reasonably well with Wine as well these days (it used to be crap). Intel needs to fix their drivers.
Roderick