The article is not well written, and I personally had to parse it several times to figure out what he was trying to say. I'm still not even sure if this is the correct interpretation.
> Believing that an air gap exists or will continue to exist indefinitely is hence setting yourself up for some unpleasant surprises in the future, and encourages weak security designs where the network/system is crunchy on the outside and all delicious and soft and gooey on the inside. (Which is more secure, to have your local WiFi set up with WPA or whatever and have employees telnet into servers, or just go Google-style and have fully encrypted end to end links without requiring any belief in security of the links?)
That depends on your physical security. A facility like the one he described should have had regular security audits to verify that no hard lines were placed where they should not be. All hard lines and ports should have been marked with identifying information. Nobody should have been able to keep a line open for any significant period of time unless these processes broke down.