The core is "Why", then it's layered with "What", and surrounded by "How".
I reflected on my career so far, I started as a "How" person. My team lead would ask me to take on a project and I would complete the project because I know "How" to do it.
As I got more experience, I became like a "What" person. I analyzed the scope of the project, define "What" needed to be done, then delegated the "How" tasks to others.
Now I am working my way to become a "Why" person from a "What" person. I might never become the "Why" person, but I am hoping one day I will be.
Just as the book said, there are not many "Why" people in the world, but I am more than happy if I can be the "What" person for the "Why" people.