I will start by giving a brief overview of the proportional hazards assumption (focusing on Cox regression) and discuss the 2020 paper by Mats Stensrud and Miguel Hernán "Why Test for Proportional Hazards?" (https://doi.org/10.1001/jama.2020.1267). Their statement that ‘statistical tests for proportional hazards are unnecessary’ is potentially controversial, but I don't disagree. I am concerned that the statement may be (mis)interpreted by some as ‘assessing proportional hazards is unnecessary’.