There's some truth in what you're saying. Let's see if we can unpack the ideas. The largest component of the HF universe is L/S equity. The hedge ratio used by a L/S equity fund is a random variable. When markets are trending up strongly they reduce their hedge ratio to capture more beta. Typically, L/S has a net exposure of 0% to 40%. Given the current market trend many are probably running close to +40, hence, your point about being highly correlated at the moment. As an aside, the typical L/S short portfolio is a blend of ETFs or shadow indexing.