The traditional methods for modelling the electronic excitation in direct simulation Monte Carlo (DSMC) simulations treat each internal mode individually and disregard any interaction between modes. To address this, a vibronic model was developed by Civrais et al. (Phys. Fluids 36:086112, 2024) allowing each electronic excited state to excite its unique vibrational quantum levels. This work expands on previous work by providing complementary physical insights into the modelling of the vibrational quantum levels of electronic states. The fundamental differences between the uncoupled and coupled approaches in terms of the internal energies and distribution functions are outlined. Then, the scalability of the vibronic model against the traditional approach is demonstrated for elementary operations. It is shown that the coupled approach demonstrates a comparable runtime as the uncoupled approach. Finally, the traditional uncoupled and coupled approaches are applied to the modelling of the electronic excited states on the forebody of the Space Shuttle at an altitude of 99.49 km, demonstrating the inaccuracy of the traditional assumption of the electronic excited states being distributed according to the Boltzmann statistics. It is also shown that the population of the electronic excited states and their vibrational quantum levels strongly deviate between the two approaches, suggesting a significant impact on the line intensity of molecular species’ absorption spectrum.