The first experience was a proper one only because Atlas happened to encounter a God whom he was somewhat related to.
Purgatory was never meant to be a place where one could experience any kind of emotion, including suffering and misery. Entering the afterlife was never meant to be a calm or exciting experience for a soul, especially not for a living one.
When Atlas was swallowed by the jaws of Ammit, the darkness around him became physical. A ground appeared below him, which was the only indication he had that he was back in that place.
And in that place, there was nothing he could do but wander aimlessly, trying his best to keep his mind together.
This time, it was different. The emptiness of this realm couldn't impact him as strongly because there was a clear image in his soul grounding him in reality.
It was the image of Anubis using his power. The sensation of Godly Power against his skin and soul was not easily forgotten.