I would have to guess it's an overlap between "what we don't know" and "what we think we know", which is a bit easier to justify than the diagram in the article

I would have to guess it's an overlap between "what we don't know" and "what we think we know", which is a bit easier to justify than the diagram in the article. I also feel like this whole new field of "gap analysis" arose from what this article is poking fun at.