From other reading on this blog, he has a past doing assembly based game programming. It's clear from those other posts that he could care if he wanted to. But

From other reading on this blog, he has a past doing assembly based game programming. It's clear from those other posts that he could care if he wanted to. But having done his own analysis of the tradeoffs, he doesn't find if valuable to worry about performance overly for the kinds of problems he now works on.