E. Vázquez-Semadeni, A. Palau, J. Ballesteros-Paredes, G. Gómez, and M. Zamora-Avilés. (2019)cite arxiv:1903.11247Comment: Submitted to MNRAS. Comments welcome. Section 6.7.3 contains a rebuttal to recent criticisms to the scenario raised by Krumholz et al. (arXiv:1812.01615). Abstract abridged.