Originally Posted by
Absimiliard
There's no telling if they've decided on a retcon by now or not, but the lifestream was stated a long time ago to operate in much the same way it does in FFVII. Every creature receives a tiny amount of lifestream at birth. The quality and quantity of this lifestream increases over the course of the entity's life before being reabsorbed in totality after their mortal demise. Everything they are - memories, abilities, identity - is stripped away, their contribution allowing the lifestream to gradually increase with time.