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

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.