Kids cant find a way if they dont have access to a phone.

To be able to do this they need unrestricted access to a smart phone in their personal time. This is something parents very much can control for 10-12yr olds.

>Kids just don't understand the effects that it has on them

Neither does anybody else since it's not settled science. And even then it's questionable how much you can trust the science due to the replication crisis.

My parents believed that sitting too close to the TV ruined my eyesight, rather than it being an indicator that I needed glasses.

You enable parental control on the phone before you give it to your kid. Then you can easily manage allowed applications/web sites and screen time.

As the father of two children who grew up with the Internet, which I restricted for them, and grandfather of five, one of which is 13, I would say yes, parents always have the ultimate say in it.

A child shouldn't even have a smartphone IMO.

Of course they have a say in it. It’s bordering on neglect to give a 10 year old that junk.