For the education oriented audience you need to explain everything, in some good order of revelation. Ideally not all at once. What is it that we are calling "shell"? Why is it called that? Where does it come from? Why are there different kinds of these things? Why do we go out of our way to install some other one intended for some other system? What's Linux?
This author doesn't have a chance in a room full of newbies. You have to have your technical dope straight, and it's not enough.
It is often best to present a problem or a definition in a simplified way. After grasping the basics, we can extend or go into more depth. Otherwise, students can’t see the forest for the trees. Of course it is still important to state that the definition is presented in a simplified form.
I disagree with all of them from an educational point of view.
Having said that, it helps to clarify whether the audience is technical or education oriented. The title implies a technical book, so I'm with you on the comments.