Sure but is that evidence that content type does not matter?
My point is to distinguish what young children do with their screens: they could be learning things through educational games or videos for example.
Me, I'd hypothesize little if any difference between the rare encyclopedia-reading 4-year-old and the drivel-watching 4-year-old, as my personal unscientific belief is that it's about socialization with family and peers, not content.
But I'd be super interested in science teasing apart those effects.
If your position is just "most parents suck, who needs evidence?", that's valid too, but IMO less interesting than understanding what's really going on.