The new feature is created to let parents control who their children can communicate on their phone. I'm not sure if you have to play with any more settings (via the "Always Allowed") section, like pulling Messages and FaceTime from the list of allowed apps, but CNBC notes that simply enabling Downtime should be enough to remove that link that allows your kid to add unknown numbers to their contacts-at least, during downtime.
The issue only works when contacts aren't stored on iCloud. Bullies and strangers are among the threats that Communication Limits was created to address.
Better yet, if your baller child also has an Apple Watch, they can simply ask Siri-on the watch-to call or text a number. It does not matter if the number is in the contacts list or not.
The workaround for this bug, that the parents can use for now is to sync the contacts of the Apple devices to iCloud.
In a statement for CNBC, Apple called syncing contacts to other services a "non-standard configuration", although users should be able to have alternatives and still benefit from the phone features delivered by the maker. To access the parental control settings, you can head to the Communication Limits tab inside of the Screen Time settings.