Incidentally I was struck recently by how rarely in this talk[1] Jon Blow says 'children' or 'kids' when he's clearly talking about young humans. Instead it's just 'people'. :)
Haven't read the study (and tbh I'm skeptical of such scientism, e.g. reading too much into FMRI tea leaves). But perhaps one thing in the mix here, if there is indeed an effect, is that kids who get more time to themselves to pursue what's interesting to them and play, away from meddling adults who know what's better for them, develop faster.
Or indeed kids whose parents share their interests and play with them.
[1] Video Games and the Future of Education: https://www.youtube.com/watch?v=qWFScmtiC44