This is quite old, and paints an overly rosy picture. After this was published a lot of the SteamBox project people got canned and were less impressed with the reality of Valve:
"We were having a difficult time recruiting folks. We would interview very talented people but they would be rejected by the old timers at Valve as not fitting the culture."
This sounds like a terrible environment to develop in.
This quote was talking about the Steam Box team, a hardware team that was an enclave inside of a software company. It sounds really hokey for this team developing new hardware to be unable to bring in necessary talent for whatever reason.
It might be different if the new hires did have day-to-day work with these old software or video game developing fogies.
This sort of outcome is what I find so frustrating about how some in tech just refuse to believe that humans act a certain way in groups and organizations. Like, oh, management structures have failure modes, so let's just not have one. But that's not enough. You just end up with a de facto structure that no one can talk about because it's not written down anywhere, is not beholden to any formal rules, and most likely operates in private, in groups that you're not invited to.
http://www.wired.com/2013/07/wireduk-valve-jeri-ellsworth/