Sam isn't giving general career advice here -- read this advice as if you're giving it to a risk-seeking, ambitious, 19-year old (the title of the article...).
In that context -- his advice makes perfect sense.
The article isn't explicitly directed at "risk-seekers," but merely at ambitious people. It's incorrect to conflate the two. Ambition can just easily manifest itself as a desire to seek a large salary, climb the corporate hierarchy, and seek a nice lifestyle. As a member of the cohort at which this piece was directed, I don't know why everyone assumes that we want to expose ourselves to risk, or why everyone asserts that we ought to.
Why does everyone exhort the necessity of risking everything in an attempt to change the world? What is so bad about simply pursuing a nice life?
three kids, a safe job, two Ferraris, and the ear of Larry Ellison?
or how about
Climb the ladder, eventually transition to politics, and become a Senator on a technical platform?
ruswick's point is that ambition is not the sole province of the startup crowd.