From a recent conversation between Sephiroth1999AD and Kawaii Ryűkishi

Sephiroth1999AD: I noticed that there's two different ways how "Chapter 5 Complete!" message can appear.
Kishiruni: Yeah?
Sephiroth1999AD: 1) Shuyin and Lenne are embracing each other, and as they fade away, the Chapter 5 Complete message appears
2) Shuyin and Lenne fade away, and your characters start leaving the Farplane Abyss. They go and check up at Nooj, Baralai, Gippal, Leblanc, Ormi and Logos, and then "Chapter 5 Complete!" appears.
Kishiruni: What do you have to do to trigger either one?
Sephiroth1999AD: I don't know. I was hoping you'd know. I prefer event 1) myself.
Kishiruni: That's the one I got, yeah.
Sephiroth1999AD: The first time I played, I got 1). When I loaded the game, I think I got 1) again, but after that, I've got 2) a lot.
Kishiruni: Maybe it depends on how the last battles go.
Sephiroth1999AD: I wonder if it has something to do with whether you talk with other characters or return to the save point after the long dialogue before the final battle (before you fight Vegnagun's tail)
Kishiruni: Could be. I don't think I've ever gone back.
Sephiroth1999AD: Hmm... the first time I played, I went back.
So does anyone know what triggers the way how "Chapter 5 Complete!" message appears?