Quasi‐classical trajectory (QCT) calculations were conducted to analyse the influence of vibrational versus translational energy in promoting reactivity, and the impact of vibrational excitation. The investigation revealed that independent vibrational excitation of ethane’s symmetric and asymmetric stretching modes (differing by only 15 cm‑1) yielded comparable reaction cross‐sections, HCN(v) vibrational product distributions, and scattering distributions. This observation dismisses any significant mode selectivity. Moreover, an equivalent amount of energy provided as translational energy gave rise to slightly lower reactivity compared to the same amount of energy provided as vibrational energy. This effect is more evident at low energies, presenting a counterintuitive scenario in an ‘early transition state’ reaction. These findings challenge the application of Polanyi's rules in polyatomic systems. Our calculations reveal that the reaction cross‐section remains practically unaffected by CN vibrational excitation, suggesting that the CN stretching is a spectator mode. The results were rationalized by considering the coupling between different vibrational modes, between vibrational modes and the reaction coordinate, and a significant vibrational energy redistribution before collision, that creates an unphysical energy flow, resulting in loss of adiabaticity and vibrational memory before the reactants’ collision. These theoretical findings require future confirmation through experimental or theoretical quantum mechanical studies.