I completely forgot to bring up the 2600 section in my post! Reading distance dialing led me down a deep rabbit hole. An interesting path was learning more about Joe Engressia (Joybubbles) who could whistle a 2600hz tone to circumvent the supervisory tone which led him to learn more about the system and further the knowledge of the early phreaking community. Folklore around him was off the charts and eventually painted a picture of a superhero who could whistle his way through the whole phone network and into free calls to anywhere just with his mouth. The document linked in my post gives details about the long-distance signalling and why being a great whistler was not good enough. That said, definitely check out more about Engressia, because while the whistling wasn't superhuman, the curiousity and drive to learn more may have been!