For those not familiar with the reasons why Steam on Linux games aren't more frequently benchmarked on Phoronix as part of our graphics testing but tend to benchmark older titles and non-Steam games, read Finally, Team Fortress 2 Benchmarks For Phoronix! and Running Benchmarks On Other New Linux Games. Long story short, tests run at Phoronix must meet strict requirements for reproducibility and turn-key deployment capabilities... This is just not to save me time with constantly benchmarking new Linux software and hardware, but also to make it reproducible to third-parties wishing to verify the test results or to carry out similar tests within different environments.
All testing is automated via the open-source Phoronix Test Suite software with OpenBenchmarking.org to deliver the best Linux benchmarking experience. This just isn't about self-promotion but nearly all major IHVs and ISVs using the Phoronix Test Suite internally in some fashion.
The good news now is that I've heard from a Valve Linux developer that additions to the Steam API will finally allow us to at least record universally a build revision/number for each game... Up to now it's been rather hard to tell if two separate copies of a Steam game being benchmarked were actually the same version (and thus comparable) or not since there wasn't an expressed build number across the board of all Steam games. With the latest Steam API work, it looks like we finally have that ability to record a build number for Steam games to make sure the same version of a game is being benchmarked.
Unfortunately, there's nothing much that can be done from Valve's end for being able to fetch older versions of a game -- if you wish to see how your modern hardware is doing against a Phoronix article with results from a few months ago, how new drivers are comparing to an older release of a game where older drivers were benchmarked at length, etc. There isn't much in the way of revision control capabilities on Steam for rolling back to an older version of a game and it doesn't appear there will be that capability added due to size/interface restraints.
Beyond the work to be able to expose build/version information, there might be some news shortly on another front when it comes to playing back OpenGL traces of popular proprietary game titles via APITrace and VOGL... Stay tuned for hopeful more information in the days ahead. At least for Valve games I already have assurance of being able to use their OpenGL traces without concern for copyright/license matters.