I think things have shifted a bit away from that. IIRC, AMD's pretty free with the documentation for everything that isn't part of the DRM-enforcement chain, so their open source drivers are mostly lacking in manpower. NVidia just won't release the docs at all, so the open source drivers for them are reverse-engineered and plagued by problems like an inability to get most GPUs out of power-saving mode. I'm not sure how open Intel's documentation is, but their only Linux driver is the open-source one that they do significant in-house work on and it has often been competitive with the Windows driver.