I think it's probably just very, very unlikely that any individual person individually knows a representative sample of divorced couples, and within what sample

I think it's probably just very, very unlikely that any individual person individually knows a representative sample of divorced couples, and within what sample there is the original commenter noted that the father contesting custody was a subset. I think people also maybe aren't primed to think of this in terms of "What percentage of people who contest custody receive custody, by gender?" They're just thinking to themselves "Of the couples I know who are divorced, in what percentage does the woman have custody?", and that is going to be very large because a very small percentage of men contest custody. Anecdotally, almost every divorced couple I know has had child custody with the woman (I am in Australia, for the record). The much smaller subset of "divorced couples where I know the father contested custody" are two father's with custody and one mother. Obviously, those are also the only divorced couples I know where the man has custody - no court is going to give custody for a child to someone who doesn't want it, ideally. I also know a lesbian couple who've gone through a custody dispute but I don't believe that really has any impact here.