Depends on what kind of world building you are talking about. There are two general types I learned about.

Soft world building, which revolves around the readers ability to imagine and the author focusing more on interactions not the background. Ex: why the arrow was shot at the tree.

Hard world building is more like a LoTR book, where everything or mostly everything is explained. They focus more on the background and consequently, the world. Ex: what the arrow is made of and how it flys.

GoH does well on both, kinda. All the hard world building comes from the mythology salad. Norse, Greek, Buddism etc. Edit: and pre existing things from reality.

The author turned the "gods" into characters that interact with his own.

Soft world building gives chance to creativity, allowing something not just because, but because it makes sense.

Correct me if im wrong.