See how another regular pentagon is formed where the vertices are all vertices of the dodeca? This pentagon has sides of length phi times that of the dodeca's edge lengths. There are 12 such pentagons formed from the ratcheting of the cube (i.e. the five cubes nested in the dodeca). The 5 sides of each pentagon is formed by an edges of the 5 cubes, one from each. The 72º angle we ratchet successively through is also intimately connected with phi. It happens to be two of the angles of the golden triangle where the side to base ratio is phi. Five and phi-ness and phi-ness means the square root of 5. There is still much more.
Where there is a nested cube in the dodeca, there is a nested tetra. So not only are there 5 unique cubes in the dodeca, there are also 5 unique tetrahedrons, each corresponding to a unique orientation of one of the 5 cubes nested in the dodeca. But an octa is nested in a tetra nested in a cube so each of the 5 cubes and 5 tetras are associated with a unique orientation of the octahedron with respect to the dodeca.
The same does not hold true for the icosahedron within this unique nesting of Platonic solids. This is because of the fivefold symmetry of the icosa and its orientation with respect to the dodeca in this nested set. After every 72º rotation, the icosa will be oriented in exactly the same way with respect to the dodeca as it was before the rotation. i.e. The icosa will look as if it has not rotated at all unlike the other three Platonic solids.
The slideshow below illustrates some of the various configurations just mentioned. There are 6 images set on manual advance for your viewing leisure. Click on the arrows to advance forward or backward in the image set.