I'm not really sure. I ran into it while trying to setup intel in my gentoo. Just like a lot of other users, I tried a lot of different versions of everything and couldn't achieve what was working fine in Ubuntu. In the end I decided to just wait until the official intel driver matures enough and now it's pretty usable (intel-2.5.1 with xorg-server-1.5.2 and mesa-7.2). Ubuntu used a lot older stuff but patched with "something".
I used a lot of google and went through forums of pretty much every distro this way. No one knew how it worked.
Yeah, they do that; I have one proof. They patch their i810 driver, or patched when it was still included as an alternative, with new pci id's to enable it to support 945 and 965. It was just a small change, but when people for who intel didn't work tried to use i810, and it didn't work like in ubuntu..
So you claim that they identify a bug, take the time to fix it, report it and then don't send the patch? I hope you realize how ridiculous this sounds.
Yes, there have been issues with Debian in the past - but those were about the quality of the patches Ubuntu sent, not about failing to send the fixes! Yes, there are people who believe Ubuntu should be more involved in kernel development - even though Canonical lacks the manpower and technical expertise to help.
But please, don't claim they don't cooperate with upstream. That's the whole freaking point of Launchpad!
If this has either changed or never was true then I really, truly am sorry (and apologise) for spreading this information.
That said, when I was trying to make xorg work 3 months ago and read a lot of threads, blog entries, list archives and such stuff, I found this information quite a few times (and the authors where not proved wrong/accused of stating not true/etc. by any one) I simply took it as a fact. Also I'm sure that if those patches would make it's way upstream, they would in the Xorg's GIT and patched versions would be available at least in the Gentoo x11 overlay. The fact was that no one there knew how to make it work.