I think you missed a few things.
Long-short is not a substitute for long-only. Two totally different strategies.
A short extension strategy can be viewed as a substitute for a long-short strategy. An entity may have restrictions that prevent it from investing in alternatives (structural), lack the adequate capital to meet minimum subscription amounts for HF’s, lack the size to maintain a diversified portfolio of alternatives (<$100MM), etc.
In that instance a short-extension strategy (see 130/30 marketed by mutual funds) can act as a substitute for a long-short strategy. Not to go outside the scope of the text but accreditation is a factor for individual investors.
Long-only is off in its own land.