That's roughly one every other hour, so still not quite on the same level. And we do use tooling _in addition_ to GitHub, but reviews are done in PR and not over email.
(FWIW I personally wish more projects worked like the kernel's, but such is life)
By the way, we've been succesfully using Gerrit on smaller-scale projects as well (around 8 change-requests / day) and don't even want to think about going back to pull-requests.
Criticisms in the interview were essentially about low discipline that Github interface allows, and how they were not willing to adapt to the kernel needs, not about fundamental deficiencies of pull request based model.
So far nothing has been said about why pull requests via a website might handle less load than pull requests over email.
http://www.mcvoy.com/lm/bitmover/lm/talks/socal/
tl;dr: fan in/fan out scales great if you have BitKeeper or Git.
Github doesn't scale at all for large projects. The kernel is averaging over 8 changes an hour, 24 hours a day. That rate of change can never be handled by doing pull requests and web site review. It only can work with email and review and scriptable processes.