Their exposure will still be much less than someone who gives them free reign and lets them sit in the livingroom staring at a phone. They won't be staring at the phone distracted while they're hanging out with the family.
No it’s not. Everyone hid things from their parents. I hid soooo much from my parents. It’s fine. It’s normal. It’s far more important to have limited exposure to modern smart phones.
What, exactly, is so problematic about not telling your parents that you smoke weed with your friends before playing video games? What, exactly, is so problematic about not telling your parents who are dangerously religious, that you had sex with your high school girlfriend? These are all normal, innocuous activities of teenagers. A therapist would not think twice about hearing them.