The purpose of the faces/trucks data point is just to illustrate that these differences start from birth. The larger argument is that the people-vs-things gap, and later, interest in computers specifically, basically remains stable throughout childhood, adolescence, and early adulthood: https://slatestarcodex.com/2017/08/07/contra-grant-on-exagge...

I don't even know if the data is ready for us to draw any conclusions, but at the very least it seems to me we should find this to be an extremely interesting pattern, and use it to motivate hypotheses.