The study didn't plot the entire state space. It's simply a map of the end state of a limited space of parameters (specifically, the mass of the objects is fixe

The study didn't plot the entire state space. It's simply a map of the end state of a limited space of parameters (specifically, the mass of the objects is fixed, two of them are in a particular orbit, and basically only the angle and timing of when the third object approaches is varied). The plot just shows which object gets thrown out of the system for each initial configuration.