The aril of the yew berry, yeah. Or flesh I suppose. True, eating leaves is different.Yup, but that is not at all like eating the plant itself. Even there is some selectivity as some berries are poisonous to some animals and not to others. Then there is the case of the pulp(?) being edible but seeds poisonous like yew. Even there we have selection as some cultivated berries are the result of selective breeding to get rid of things like saponins.
Would saponins in mashed leaves rise to the top when boiled? That would pose a problem for leaf curd.