These are the words used to describe how a narrow focus leads to leverage in our efforts to earn visibility for our work. They all describe going narrow, small, and focused to increase impact.
It's easier to narrow the area over which we apply force than it is for solopreneurs to increase the amount of force.
Impact = Force / Area
That's one way to think about the reason why narrow focus increases impact.
Another is in terms of relevance.
Potential Relevance = Homogeneity of Audience
Focus is necessary to create relevance, and relevance is the prerequisite to visibility.
Either way you think about it, indie consultants who are successful at earning visibility have invested in learning about who (they are trying to connect with), what (is relevant to them), and why (buyers will care enough to take action). This investment and learning leads them to focus. They cannot answer the foundational questions of visibility (who, what, why) if they do not focus in some way.
If who is everybody, and what is everything, then the answer to "Why would buyers want to know about you?" is: they won't.
Narrowing your focus makes it easier to earn visibility.