Think of them as peaks and nodes of an impulse model for a convolution reverb. As complicated as that sounds, that's exactly how expensive reverbs model famous rooms' acoustic characteristics. However, that test is far from an accurate respresentation on how body shape will affect overall tone because it is testing merely an impact resonance and not vibrational torsion from the strings being played. Simple mechanical physics dictates that differently shaped wooden bodies are going to resonate differently without the graphs. All those tests showed was where in their bodies that resonance flexing occurs.
