If you’d asked me for the password to my kids’ phones, I would have had no way of knowing what they were.
I’m sure he doesn’t know what the passcode is. But the phone is in his name and with his permission, the phone manufacturer can break the passcode. He will not allow it.
Passwords are useful if you tend to put the phone in your back pocket. They keep you from accidentally dialing someone by sitting down.
However, I made my daughters remove the password on their phones. I told them I’d never violate their privacy, but if, God forbid, they were in an accident, or unconscious, police or a friend could get to the contact list quickly to make a call. They seemed quite satisfied with that explanation.