Child can access internet through settings app when screen time is blocked

I have screen time on my sons phone. All of the apps are locked at a certain hour. The only app that is accessible is the “settings” app. However if you go to General-About-Certificate Trust Settings you can access the internet and this is unmonitored. Even though Safari is disabled. You can access the internet really through any app that has a link to an external website. How can this be prevented? I’d like to lock ALL APPS including the settings app so that nothing can be touched after a certain hours.