Agreed, and your had a more easy example at hand, XBox DirectX, versus the PC world.
The point is that many that argue Khronos APIs are portable, don't seem to have deal how portable they actually are in practice, just like POSIX is portable only to certain extent, or Web standards (which then many just ship Chrome with their app).
The point is that many that argue Khronos APIs are portable, don't seem to have deal how portable they actually are in practice, just like POSIX is portable only to certain extent, or Web standards (which then many just ship Chrome with their app).