Saying that you should learn the terminal because a machine may not have Atom or Sublime is sort of saying that an advantage of the terminal is that you don't have to install additional software, isn't it?
That said, being able to work with standard tools is extremely relevant for debugging problems, still.
There are many environments that are CLI only. That’s what the author is talking about. You’re talking about environments that don’t allow you to install apps. That’s a completely different discussion.