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.

It's just a simple AM broadcast. It was only novel at the time because radio was new.

Uhm, broadcast on the same frequency? It's not that hard to figure out what frequency Marconi was broadcasting on.