That inadvertent confirmation of iOS 13.3's imminent release was on the mark. Apple has released the new software (plus iPadOS 13.3), whose centerpiece is an improvement to Screen Time parental controls. You can set limits on who your kids can call, text or FaceTime, including managing contacts and setting time-specific limits. If you don't want your kids starting video chats with friends after 9PM, for instance, you can. This won't help if your kids use third-party apps, but it's a start.