They aren't really talking about a ban. They're talking about introducing 'kids phones'.
Korea essentially solves this with their ID system. It doesn't matter what the phone is, its the owner that is inherently an adult or a child. Since all sign ups require you verify your identity through your phone, when someone puts in their name and phone number on a site, the site connects to a database and can verify if it's an adult or child's phone and whether or not it belongs to them since it asks the database if the name and number supplied to the phone matches.
Unless they're going to start arresting kids under 16 because they have an 'adult' phone, this seems pretty pointless.