b. High scale Design System in a virtual world.
As said earlier, in such big games, creating an experience does not mean to design a single product, but a multitude of "products within the product" that are all parts of a different bigger world and story than ours.
A coherence of interaction within a product is the goal to achieve as a UX designer, but it can be even more complex in a game, where each interface has a different purpose/location. They are all unique and conceived by different designers and artists from different specialties, but are a part of a bigger picture and must remain coherent in it.
Game UX designers have to develop a design system and models of interactions that remain constant while being used with different controllers, in variable situations at different levels of the game.