I don't think the advice is "learn to code", as such; rather, the author's saying "be prepared to do whatever your business needs to be successful." Obviously the CEO shouldn't be writing a lot of code in the long run, but at a startup, everyone needs to be prepared to do whatever needs to be done, not necessarily what their job description defines. Hiring "web guys, a marketing team, science advisors, customer support people", etc. makes sense in the long run, but a CEO who only views his role as managing others + "the vision thing" and isn't prepared to get his hands dirty, probably isn't a great early-stage startup CEO.