There are a number of studies that show that Grit is either not a thing or there are better measures of success. It has been a long time since I have thought about it so I don't remember which papers in particular.

Also, it can be argued the author was either playing fast and loose or knowingly misleading readers with her statistics: https://www.npr.org/sections/ed/2016/05/25/479172868/angela-...

If you like Podcasts the "If Books Could Kill" Podcast goes into some of this story again too.