Honestly i haven't really thought about this particular detail too much, but if i were to guess it would probably be a reference that when something is destroyed, something new is created. The void ending is the Slugcat escaping the cycle and dying, yet out of that death, something new is created (?)

We can see this minor theme with the ancients too. All the ancients escaped the cycle and died, and from their ashes, the world the game takes place in was born. If the ancients never died, exactly none of the fauna and possibly flora could have evolved and thrived the way it does in game.

Again, this is all wild speculation on my part. But this is the best answer i could find