With an improved Boltzmann-Uehling-Uhlenbeck (BUU) model, we have performed a comparative study of the reaction dynamics which limits the formation of fusionlike residues in 40Ar + 27Al collisions at energies near the Fermi energy. By adjusting separately the values of the in-medium nucleon-nucleon cross section σNN, we have obtained similar residue cross sections for both the stiff and the soft equations of state (EOS). Using these two exclusive parameters, we have calculated the thermal excitation energies, the angular momenta, and the temperatures for the fusionlike residues survived in the collisions. These calculations suggest that the reaction dynamics, not the Coulomb or thermal instabilities, plays the most important role in limiting the production of fusionlike residues at energies less than the Fermi energy. Furthermore, the calculations indicate that although the same residue cross sections can be obtained for different equations of state by adjusting separately the values of σNN, one would still see significant differences in the residue temperatures. This sensitivity to the temperature arises from the sole sensitivity of the temperature to the EOS and the insensitivity of the temperature to the σNN. Within the uncertainties of both the experimental data and the model calculations, the calculated residue cross sections and the residue temperatures are comparable to experimental observations. More systematical experimental studies, including the impact-parameter dependences, are called for, in particular, to address the questions concerning the equation of state.