If this is true this is just an excuse. AMD devs are not forced in any way to use only ubuntu to do development. Just to remind: NVIDIA support the lastest Xorg, usually before the stable release (at least with a beta driver, QA is not quick and this is good) and more over they support a lot more OS than AMD. Intel supports Windows and Linux as AMD and their driver just works with every version of Xorg, being it even the most bleeding edge git branch. Indeed it does, it is an open source driver. The radeon driver does the same, with the difference the intel driver has a more high support level.
Originally Posted by AlbertP
In other words AMD is in the middle between NVIDIA and Intel, with the sum of doing two half working or half supported driver, i.e. the worst situation for all users. I will be very very happy if AMD will follow the intel way in the future and put more effort on the radeon driver (btw, the radeon team already does wonders being it so small), but it will be usable even with NVIDIA way, it is not the best, but still works.