I assume a negative correlation too. The insolubility between the water and the oil must avoid the oil absorption. On the other hand, the water could react with the oil to produce Fatty acids and reduce the oil quality.
It is vital to avoid the presence of water during absorption. It is known that the oil is not soluble in water, so the absorption decreases. On the other hand the presence of water favors the hydrolysis and saponification of the oil forming free fatty acids and soaps respectively
Its better to mix oil in complete dried pellets, you can keep feeds in oven for sometimes to remove the moisture and should not prepared bulk amount at a time which reduce the feed quality.