Nobody is saying that. They can (and do) consider it theirs but their parents ultimately have the final say about how they're allowed to use it. Stronger protections would simply bar OEMs from imposing restrictions over how we're allowed to use our own devices.
You made the argument claiming that freedom of choice and strong ownership rights will inherently allow kids to bypass parental controls when that's obviously not the case. A device can always be locked down by its legal owner or by someone's legal guardian who has a duty of care for that person. This sort of bad faith concern trolling has gotten out of hand.