If you're only going by the short snippet lordnacho quoted, yes it might seem like it's just "culture". Culture would be shared rituals like language, food pre

If you're only going by the short snippet lordnacho quoted, yes it might seem like it's just "culture". Culture would be shared rituals like language, food preferences, music etc. YNH's "shared fiction" idea is about humans' ability to deliberately create new abstract entities that compels humans to act together in service of that entity. Examples of his shared fictions would be a "company" or "fiat money". These "fictions" somehow organize humans to cooperate and multiply their power over the world. Culture, on the other hand, like regional food recipes, would accumulate organically and accidentally.