Eating morgia roots is less likely to increase Willpower if the attribute is increased by items/corruptions or temporarily boosted. For example, eating 4 of the herbs with a base score of 12 and no boosts will almost always result in a Willpower increase, while eating 4 of the herbs with a base score of 12 boosted to 99 will rarely result in a Willpower increase. Given that whether or not the training can work at all only depends on the base score, this seems like incorrect behavior.