Not quite. Nobody I know speculates the bridge of the ACX Crystal was deserted. There is a general assumption there was at least one person on the bridge of the ACX Crystal, because even the laxest of civilian crews would not violate that law (I believe the law states there has to be someone there anytime the ship is in motion)
What we don't know is if that person was actually paying attention, surfing porn, watching a movie on a laptop, or reading a book. We just don't know.
But if you look, the ACX Crystal did make a course change to port of a couple of degrees at around 0120 local time (about ten minutes before the collision) so it is plausible that there is some credibility to this.
But...signaling with lights? As another poster said, I would expect a horn, never mind simple verbal communication.
That said, the captain of the ACX Crystal might have been using the known public domain tracking of his course, and used the course change that occurred as a matter of programming to send a message by signal lamp because...well...there wouldn't be a concrete recording or record of that...right? What if they look a the logs of the ACX Crystal? That WOULD and SHOULD most definitely be a log entry. I smell a bit of ass-covering BS by the ACX Crytal.
Actually 13-14 minutes before.
and No there is a very good explanation of that course change.
Crystal waa on the southern edge of the Traffic Separation lane, which means Fitzgerald crossed the lane without noticing that every Merchantman there was making the turn
Everything that has come out indicates the ACX Crystal was sailing properly.