Earlier quoted context omitted.
I'm pretty sure this parenting advice was based on a psychological experiment that failed to replicate.
You may be right about some particular study, but in general, there is a lot of research around growth mindset, and I have not heard about failures to replicate (though I cannot vouch that they haven't happened): https://slatestarcodex.com/2015/04/08/no-clarity-around-grow... .
Last I heard, which could be outdated, is most of the popular experiments have failed to replicate to a good measure. Odds are, if you just heard of an experiment, it hasn't replicated. Worse, many of the studies were propping each other up. So that when one failed to replicate, it brought the others into question.