Well, it's put in a bit of a disrespectful tone, but I think you are right. Unrestricted access to a smartphone will lead to 6 hours + a day screen time. And it's all addictive junk. That can't be good.

One also sees the "educational" difference. Here a study was published concluding that poorer areas have twice the number of snackbars compared to areas with "higher educated" people. Bad food is also very cheap. It's also very easy to never read about the effects of screens on childeren and I see people with kids of ~1 sitting on the back of a bike with a smartphone blaring... Why not let the kid enjoy and learn from the surroundings? My kids loved riding a bike with me.