Showrunner Dave Filoni falou sobre isso em uma entrevista à IGN. Em suma, a combinação de seus restos físicos e sua presença na Força, devido à sua morte na cela, cria uma estranha mistura de essência e presença que parece estranha, mas ainda é suficientemente atraente para aspirantes a resgate de Jedi.
Filoni: Literally, what you see in that hologram, is her sitting, waiting to be executed. It’s a recording of that event. So when they walk in and see her, they’re actually standing where the Inquisitor was standing [when it was recorded]. And so when she walks up and looks at them kind of distantly and not very friendly, she’s looking at the Inquisitor and that’s what the recording is of. Then she steps over into that chamber and obviously she gets killed there. It’s really wicked when you think about it. The material of her body is the essence that Kanan is somehow sensing through the Force. But he knows there’s something off about it. But since he didn’t really know Luminara, he doesn’t really know. That’s one of the interesting things about death and then the dark side and all these different ways you can use the Force. The sensing of people is one of the biggest dilemmas, I think, in all of Star Wars, because people want to use it like a metal detector.
STAR WARS REBELS: DAVE FILONI ON THE LUMINARA TWIST IN "RISE OF THE OLD MASTERS"