I think what's left unsaid and implied is that the original system wasn't secure in any way, the "tuning" was just choosing a frequency. It's only a "hack" because of the claims that were made.
In a way, that would be like advertising a secure horseback large sign delivery service, where the "security" is that the sender and receiver choose one of a few routes between locations, even though the large sign is easily seen and entirely uncovered, making the courier easily identified and the sign when in transit easily read from a distance. The "hack" for that type of system is ultimately so trivial as to be mostly uninteresting.
Nah. He just did a broad spectrum broadcast which any receiver in the area would pick up. Today, it'd probably be illegal. Tom Scott made a video about it, and mentioned that. https://www.youtube.com/watch?v=sP2qqMegNKA