Interesting. However, if one of those stations runs on a slightly different frequency, I guess its output would be garbled, correct? Like I guess SSB receiver just shifts down the band by a constant?

If it's kind of close it just sounds like someone talking in a slightly lower or higher pitch. It can still be pretty intelligible with the frequency slightly off. Eventually it gets very distorted though and you start losing a big part of the waveform entirely. Try listening in to some websdrs and you'll see what it's like.