Topical Authority
The idea that covering a subject comprehensively earns a site standing on that subject as a whole, rather than page by page. A pre-existing phrase with no single originator.
What it claims
Cover a topic thoroughly and consistently, and search systems will treat you as a source on that topic, so that individual pages benefit from the whole rather than competing alone.
The intuition is reasonable and the mechanism has never been officially documented. It behaves in practice like a useful heuristic that acquired the vocabulary of a ranking factor.
Why it matters more now
Whatever its status in classic ranking, query fan-out gives it a clearer rationale. A question expanded into a dozen sub-queries rewards a source that can answer many of them over one that answers a single phrase well.
So the advice survives the uncertainty about the mechanism, which is the most that can honestly be said for it.