Light loads has no place in EK dictionary.

If seats are empty cargo is full.
If cargo is also empty, yields are great.

Apparently DXB-SEA carries dry fruits and fruit nectar and SEA-DXB carries aircraft spare parts.

Second part is questionable based on how MRO supply chain works. An aircraft part manufacturer based in Japan won't ship all parts to Boeing Seattle to get distributed, they directly go to parts depots located though out the world. I am sure there is a valid explanation.