My daughter Theresa has lit up something in me.
In an email about the quadrants she observed that she has noticed all of them in her studies at school but that she has never seen them all together in one diagram. That got me thinking about how that is one of the most important things about the quadrants, that is that they tetra-arise and having them arranged like Wilber does points that out.
They all are happening at once in other words each moment can be viewed as having four dimensions to it. This points out that something seemingly happening in one quadrant is actually happening in all four or at least the correlates in the other quadrants have an influence.
Also she inspired me to want to create a list of examples about how having a diagram like the quadrants can be so useful.