  The recent paper by AlShebli et al. (2020) investigates the impact of
mentorship in young scientists. Among their conclusions, they state that female
prot\'eg\'es benefit more from male than female mentorship. We herein expose a
critical flaw in their methodological design that is a common issue in
Astronomy, namely "selection biases". An effect that if not treated properly
may lead to unwarranted causality claims. In their analysis, selection biases
seem to be present in the response rate of their survey (8.35%), the choice of
database, success criterion, and the overlook of the numerous drawbacks female
researchers face in academia. We discuss these issues and their implications --
one of them being the potential increase in obstacles for women in academia.
Finally, we reinforce the dangers of not considering selection bias effects in
studies aimed at retrieving causal relations.
