Okay, putting asbestos underwear on:
In most modern societies, we agree that children have limitations on the "people should be free to live their lives as they want" mindset. Otherwise, we'd be letting four year olds subsist solely on candy, hot dogs, and twenty hours a day of the Best of Elsagate.
We've traditionally trusted the compromise for that to parents. But parenting is hard. We're running on a mix of science and lore for a lot of it. Even beyond that, a lot of parents may not follow best practices, despite the best of intentions. Then add the too busy/doesn't care/actually incompetent parents.
The state has an enormous vested interest in the next generation coming out well-skilled and socially balanced. But they can't put a child development expert into every house in the country 24/7. They've had to trust parents who are spotty at best at their job, because there were limits on how they could intervene.
For the first time, we have wildly popular entertainment products that phone home and do remote work as part of normal operation. This makes a technical intervention possible in a way they couldn't do with prior moral panics (TV, comic books, bawdy novels).
In some ways, this is actually a tame and tolerant way to deal with the fear of gaming abuse. They're not saying adults can't have games, or even that kids can't-- just restricting usage when you reach a level that implies they're sacrificing something else (school, sleep, or family life) to make the hours. I wonder if a future evolution of this would integrate into directly the schools and the social credit concept-- if you can play Fortnite II: Electric Boogaloo 14 hours a day and somehow maintain straight As, it will let you, but bludgeon your character when your grades slip.