Entangled melts undergo rupture in startup uniaxial extension beyond a threshold Hencky rate. Contrary to the recent conclusion from Wagner et al. [J. Rheol. 62, 221 (2018)] that chain scission involved in melt rupture is due to an "entropic fracture" mechanism, we assert that such a fast melt extension has caused full stretching in entanglement strands, leading to sufficient enthalpic changes associated with conformational distortions at the bond level. The barrier for bond dissociation can only be lowered by enthalpic intrachain forces. The alternative explanation suggests that the more challenging task is to show how entanglement could lock up during sufficiently fast melt stretching. (C) 2018 The Society of Rheology.