iOS also has a feature to send unknown calls directly to voicemail without ringing through [0]. It seems an easy jump to classify numbers into three categories

iOS also has a feature to send unknown calls directly to voicemail without ringing through [0]. It seems an easy jump to classify numbers into three categories (known, unknown but authenticated, and unauthenticated) rather than two once reliable authentication is available. [0]: https://support.apple.com/en-us/HT207099 https://support.apple.com/en-us/HT207099