In ShieldConfigurationExtension you are overriding only the function which is responsible only for individually blocked applications. Maybe you are blocking applications based on category? Or blocking a webdomain?
Check the other functions available in ShieldConfigurationDataSource which you can override: https://developer.apple.com/documentation/managedsettingsui/shieldconfigurationdatasource
The application category shield: https://developer.apple.com/documentation/managedsettingsui/shieldconfigurationdatasource/configuration(shielding:in:)-ia14
Hope it might help, I just started experimenting with the screen time api as well!