The generally-accepted definition of a design system is that it’s the outer circle—it encompasses pattern libraries, style guides, and any other artefacts. But there’s something more. Just because you have a collection of design patterns doesn’t mean you have a design system. A system is a framework. It’s a rulebook. It’s what tells you how those patterns work together.
I agree. I tend to define a design system as the official story of how your organization designs and builds digital products. There are a lot of ingredients involved in telling that story.
A kit of UI components without accompanying philosophy, principles, guidelines, processes, and documentation is like dumping a bunch of IKEA components on the floor and saying “Here, build a dresser!” The guidelines and documentation accompanying the UI components serve as the instruction manual that come with the IKEA components to help the user properly and successfully build furniture.