It's a known issue with TWFB. I don't know if they're planning on fixing it, but most frameworks that are not in newer rounds are not appearing in older rounds any longer.
Oh, that's a shame. Why is lwan no longer in the newer rounds?
Because I failed to move the benchmark harness from the Lwan repository to the TWFB repository. Also, I'm not really spending a lot of time on Lwan any longer; there are so many things I'd like to do, and so little time. :)