Does it matter anymore? People are using less and less of the higher level stuff of OpenGL. Most of the graphics code is now in the engine. OpenGL is getting very outdated, who starting a project today would chose it over Vulcan, Directx or Metal? I would bet most small shops would prefer to use some sort of middle layer or engine from a third party. That pushes the problem of implementing the lower layers in Vulcan, DirectX or Metal to a small group of specialists.