I just finished reading and practicing the CAGED chapter in the book. It makes sense, but it seems like it should really just be CAGE. Why isn't D just considered a partial form of C?
While the D form shares the triangular shape on strings 1-3 together with the C form, the rest of the shape is unique and covers a different position. In order to understand how chords cover the guitar fretboard, and maximize the chord inversions and voicings you play, the whole CAGED template must be completed. If you just play C A G E, you skip a position before you come full circle and repeat.
All the CAGED forms have a portion of their shapes reused as the forms are connected on the neck. So you could make the same argument for any form. In time, everything will hopefully start to bleed together and you won't be confined to specific positions. At that point, you can think of them however you want.
