I'm not sure if in #6 that huge quote was part of your answer, or jsut evidence leading us in the right direction...
anyway, I remember in an interview one of the directors saying originally they did have 12 dragons, but then spilt them between the two dimensions. I think that originally there was one complete form, then split up into 6. When the timelines split, FATE was aware of this dimensional distortion of sorts, and, in attempt to further weaken them, killed off the unnecessary ones. Wrong? probably, jsut my thought though.