Maybe it´s not correct, but you can´t separate the case for rebalancing and the corridor decision:
“The with of the corridors also depends upon the client´s (especially private wealth clients) aversion to changes in the portfolio allocations. If the client is significantly averse to changes in the portfolio allocation, the widths of all the asset class corridors should be narrower than if the client is not averse. The bottom line is that we can think of risk tolerance in the conventional framework, as it applies to the variability of the portfolio´s return, OR as it applies to changing allocation corridors”. The client was averse to canging relative allocations because of certain constraints in the IPS
Furthermore, as I remember it, nothing about the correlation between gold prices and other assets were mentioned - only that gold prices were expected to increase. Because the client was averse to changes in the relative portfolio allocations the expected increase in gold prices was a risk factor. The narrow corridor was there to “trigger” a rebalancing before the portfolio weight of gold got too high.
You could say why sell if you expect gold prices to increase further. But it is not relevant in this case