I agree that the post is mistitled and should be called Why you need side projects. The two quotes at the end of the piece support this:
“If you observe a really happy man you will find him building a boat, writing a symphony, educating his son, or looking for dinosaur eggs in the Gobi Desert.” - Australian psychiatrist W. Béran Wolfe
“Find a happy person, and you will find a project.” - Sonja Lyubomirsky