Ryne might be able to come back to the Source after all.

[MrThinker]

He actually specifically says that he was on the brink of death when Elidibus came and saved him.

Maybe he doesn't know he has suffered a bodily death. Cylva has been on the First for a century and hasn't aged a year, let alone a decade. The usual rules of aging don't seem to apply, and thus corporeal spirits is the most likely answer to both of these 13th survivors.