Mystery ships all over the place. We get it.
I've yet to dive deep into the murky waters of the "mystery ship" debate (but presently just lurk in the shadows) and so admittedly I am open to alternate theories. But in most things Titanic I have discovered that "Occam's razor" is often the most logical conclusion i.e. that the simplest explanation is usually the most accurate. It certainly seems that if the Californian was not the "mystery ship" then it does necessitate a rather complex explanation, as Sam so succinctly puts it. Perhaps this is an important clue.