To clarify - they won't touch the upstream packages from the developers, just backporting from "current development version" to "current stable release". This is the package auto-synced from Debian during the first couple of months in the development cycle: the Nexuiz 2.0 that is in dapper-backports was backported from edgy in (roughly) November last year, and was outdated at that time. The cycle would be:
1. Debian Games Team has a slightly-out-of date version in their repos.
2. A bit of time passes and Ubuntu automatically uploads the Debian package during the first couple of months of the six-month dev cycle, and applies the standard ubuntu patches.
3. This old version is now frozen, maybe gets backported to previous release.
4. Another three or four months passes in Ubuntu release development, no further changes to the frozen version are likely to happen, as Nexuiz is not a "main" package.
5. Stable release comes out, with a version 4-8 months old - and no further updates will happen (although backports might copy-and-paste the slightly-less-outdated packages from the next development version). Backports team hasn't bothered with backporting the feisty (2.2.1) version into edgy, because it is already outdated. Feisty will almost certainly release with this old version in April 2007.
This pattern is intended to give a good trade-off between having reasonably up-to-date packages and having packages that have been "polished" to make them reliable, and works very well for 85% of the software, is ok for another 10%, and falls down for maybe 5% of the software that is under rapid and radical development. Nexuiz falls into this category.
That is why the packages supplied for Nexuiz are so good for many linux users - you just unzip them anywhere and run the launcher.
I'll shut up now before everyone gets too bored!