Smartphones aren't the issue. You can access the internet in other ways. This feels very boomer yelling at clouds.
That said, as a recommendation, sure why not. People do seem a bit too glued to their phones overall. But I don't think that's anything new.
I also don't know anything about japanese laws, so I have no idea if this is a concern, but anything potentially enforcable that cuts into people's freedom arbitrarily makes alarm bells go off in my head.