In the first part of this series, we proposed a statisticodynamical approach of state distributions in the products of four-atom planar unimolecular reactions governed by short-range forces. In this second part, the approach is tested against quasiclassical trajectory calculations on an ab initio potential energy surface. The process considered is the fragmentation of isocyanic acid in the first excited singlet electronic state. The study leads to a very good agreement between both methods. In addition to that, we pinpoint in the barrier case the main mechanical parameters governing the shape of rotational state distributions. It appears that these parameters are related to two distinct physical effects. The first one is of the impulsive type. The second, already observed in triatomic processes, is the so-called bending effect. (C) 2004 American Institute of Physics.