The logical thing is that if they show the ghosts of someone helping us that it means that both of those ghosts/souls are there. (They helped us pulling it out) Which in turn means that Haurchefant still had his soul.

Nabriales still needed huge amount of aether from the staff and Moenbrydas aether to destroy his soul. He was sundered. Thordan was the one getting most of the aether, the rest were basically just adds. I doubt that they even have anywhere near the power. And if they had the power to just kill somebodies soul (something which is quite different to do and barely happens) why not use that power constantly in the fight to kill us?

So Haurchefant got hit by an attack, died because it pierced him, came back to help later and his body also did not disappear like any other body did when we took them out that way. I am not sure why we should just assume that SE would go so far and even destroy his souls like that.