supposedly in the new Solo movie it's going to happen. The video I watched basically said what you all have said. Either Solo bullshitting to sound good, or using black holes.
I've seen
Solo; the 12 parsecs thing does get explained in a satisfactory(and very cool) fashion. Though I did always like the old "black hole" explanation, too.
More on topic: I'd bet that Kemmler never faked his death at all. I bet he actually died, and managed to UN-die after the fact. Or at least made preparations while he was alive which allowed him to regain corporeal form after death. If anyone could figure out how to do that, it would be Kemmler. The Corpsetaker was working on doing that in
Ghost Story and (s)he was just an apprentice of Kemmler's, likely less brilliant than the teacher. Hell, Harry managed to become solid and visible while he was dead, and he started his Afterlife fairly clueless about what life was like for ex-humans.