Reading 30, Example 14: adding managed futures to the strategic asset allocation

In this example, the correlations of portfolio D with the cta indeed is higher than portfolio A and portfolio C. Then how does it critique Cassano’ s statement that adding managed futures in a portfolio of hedge funds is redundant? It a actually confirms to this statement since the corellations have increawee when managed futures are added to the portfolio as per the information provided in exhibit 33.

Need help in understanding the solution to this question.

Correlation of portfolio D with CTA is higher than for the other 2 portfolios, because portfolio D contains investment into CTA index. Portfolio C though has some HF exposure, correlation with CTA index is almost zero because the HF in Portfolio C is not managed futures it is different types of HF assets.

At least this is what I gathered from this BB, but I find it very difficult to understand.

I guess, the only way adding managed futures to the portfolio is beneficial is by increasing the portfolio mean return to volatility ratio. Corelation have no justification in this question.