Everything True Yuan Ancestor saw, Gu An could also see, but he didn't say it aloud, letting True Yuan Ancestor describe it himself.
True Yuan Ancestor's judgment was correct; the mysterious entity committing rampant slaughter in the future was indeed stealing life spans.
That is not related to Gu An's Reincarnation Body or his life span projection, but rather concerning another Saint.
The reason it is situated in the future is because that Saint has yet to step into Chaos and can only affect the future.
If Gu An were to act against the future now, that Saint's intervention in the future would vanish like a mirage, thus severing cause and effect, ensuring no trouble would ensnare him.
As for why that Saint would steal life spans, it is still unclear, but the one stealing lives and the Saint are not the same person, only closely tied by cause and effect.
More than this matter, Gu An cares about True Yuan Ancestor being able to glimpse the Saint's cause and effect.
