He's not wrong. I've been harping on this forever. I can get quench with an open chamber heads pretty easy. Getting the closed chamber head to flow is a mother bear and takes a ton of work. Especially the chamber that Chrylser used on the W5 and the CC W2 heads.
It's junk. The double quench chamber like Jpar has is a bit better but they still need some work. And I'm not just talking about flow. There is way more to it than flow.