I totally agree! "Areas of Focus" don't fit in the Horizons of Focus.
I am aware this is an old thread but it is the first one I've found with someone having the same struggles as me. I totally agree that the 20k level of focus seems inconsistent with the other levels.
I see the horizons of focus as a way of specifying a life purpose (How you would like your life to be) and then having a cascade of visions, goals and projects down from this. Having a traceable path from your projects right up through to your life purpose seems logical and makes sure your projects are building towards your goals and higher. The 20K "Areas of Focus" seems to break this chain.
I'm glad that someone else is on my wavelength as I had assumed that it must have been my lack of understanding.
My thoughts on this situation are:
"Areas of Focus" seems more like an abstract grouping (or additional source) of your projects and thus does not sit nicely in the hierarchy.
Therefore I might keep it in the "horizons of focus" but not as it's own level but as a grouping at the project 20k ft level. The areas will not only group projects for logistical purposes but also inspire projects themselves.
This fits nicely with several GTD software packages eg. Things, Nirvana etc.
Goals will now relate directly to projects.
Hope this makes sense. I would love other's feedback on this.