There was a weird thing that happened with these cars we found back in the day. I don’t remember the exact sequence, but it was something like this: turn on the headlights, turn signals, emergency flashers, and step on the brake and the radio would come on.
We did this to listen to the radio in family car without the keys. Strange things can happen when something goes wrong with wiring.
There are some years/models where the wiring arrangement allowed a backfeed of sorts when the right combination was hit. Someone posted something like you mentioned and it made sense when looking at the wiring.
