This is actually very true, but many people following this guide are looking to get google voice working, and they prefer to have a GUI such as Freepbx. Many of them may not even have much linux experience, and so they are bound to run into problems, which is why I have been trying to be helpful, and improving the guide to spell out steps further where I have seen users run into trouble.
You strike me as somebody that really knows what they are doing, and so following a simple guide that does not spell everything out would work for you because you can read between the lines and see what to do regardless. For a novice that has never touched linux, they need everything spelled out if they are going to succeed at first.