Location was chosen based on the distance and other factors.Nuian delivery point: in a contested zone where Nuians can freely attack Haranyans to defend their courier (and the NPC is inside a peace zone at the trade outlet where it's possible to safely deliver and turn in as soon as you get into the peace radius)
Haranyan delivery point: in a Nuian zone where Nuians can't be attacked (and the NPC is in the middle of the Dewstone shore where Haranyans can be attacked while getting to the NPC, while delivering and while turning in)
Why?
When Haranyans get easy start (capital right on the shore), they need to finish in the middle of the zone.
Though Nuians have difficult start (capital in the middle of the mainland), it's easy to finish as it's end is right on the shore.
It's possible to add safe zone around NPC in Dewstone Plains but it will most likely not change much.