Does Steven Soter's planetary discriminant µ1 for Neptune take into account the masses of Pluto, Orcus and other Kuiper belt objects crossing or coming very close to Neptune's orbit? If so, Neptune would probably have the smallest planet mass versus orbit mass ratio, but the lowest µ among the eight recognized planets is that of Mars. Since Mars is clearly outside the main belt, the belt cannot be applied to Mars unlike Ceres.
While Pluto, Orcus and Neptune never get close enough to each other to influence themselves, Soter obviously takes all the mass approximately around the body's orbit into account, as is the case with Ceres: for Ceres' µ Soter took the mass of the entire main belt into account, resulting in a µ of 0.33 (as Ceres has 9.39e+20 kg and the entire belt a mass of about 3e+21 kg). It is unreasonable to do that because Ceres' perihelion is 2.56 AU and its aphelion 2.98 AU, while the entire main belt stretches from 2 AU to 3.5 AU, therefore Ceres' µ is actually higher.
Soter seemingly also took the mass of the entire Kuiper belt into account when calculating Pluto's and Eris' µ, despite Pluto leaving the Kuiper belt when going towards perihelion and Eris leaving the belt even for most of its orbit when going towards aphelion.
Consequently however, Soter should have taken Pluto's and Orcus' mass into account when determining Neptune's µ, and Neptune's mass in turn when determining the µ of Orcus or Pluto. Neptune's µ is 2.4e+4 and Pluto's µ is 0.077. Do these values include the masses of the other body of those? If no, that would be inconsistent with the calculations for Ceres, obviously, as well as for Eris.