That's the issue.
And if a parent really feels their kids deserve more video game time, they can always lend their own account to their kids, which would disable the mechanism, that simple.
The government can ask video game industry to provide enforcement mechanisms in the form of parental controls, which incidentally are quite widely adopted by most tech companies without government intervention in the West.
The timeframe when a parents have a say in children's activity is already limited by compulsory k-12 schooling. What's the difference?
The difference is there is a long tail of activities that a family might be engaged in during non-school hours, especially a weekend evening. This is something a government can't possibly fathom or account for in an overarching policy.
If a person chooses to have a child, they should be deemed to have enough agency to determine what's good for them.
If a State wants to be the nanny, why stop at video games? Why not prescribe precise caloric intake, meal times, study times, sleep times, extracurriculars, and more? Just an illustration of how absurd this policy is.
But in my opinion they should have just disabled this business model completely. It seems like they want to limit the inflow of cash but not by a lot.
I don't want to start an argument on the effect and difference of fiction books / tv to games. You point is effectively that those choices may be arbitrary, however games are much more addictive than those that you've mentioned. Realistically, I've seen kids play too much games whose grades dropped like hell, but few watching too much TV, much less reading too much novel. Games can be addictive and difficult to maintain, while the same can hardly be said to TV and novels.
I agree that government-mandated limit would be too much, and less preferrable than a government-mandated system that allows parent to set the limit. You would effectively be requiring game companies to acquire and collect information on the parents of the child playing the game.
I expect a government-mandated default unless with explicit written approval from parents which would seems still rather easy to circumvent for the lack of better ways.
Current technology means statements like this are not necessarily true (these are all referring to the same story, Chinese language link last):
https://www.theregister.com/2021/07/08/tencent_facial_recogn...
https://www.nytimes.com/2021/07/08/business/video-game-facia...
https://mp.weixin.qq.com/s/Cr17TKWQ3XcuNzDw085OLw
> the new feature sees the company check accounts registered in adults’ names if
> they are playing games between 10:00PM and 8:00AM. The company will then run a
> facial recognition test and, if it identifies someone who is not the account
> holder, they’ll be booted offline. “Anyone who refuses or fails face
> verification will be treated as a minor,” according to a machine translation of
> Tencent’s QQ post.