Bone curse by default on the acolyte skills list has a red fist and a grayed out skull, indicating it does physical damage but can also be respecialised to do necrotic damage.
Harvest only has a skull implying it can only do necrotic damage, but the Crimson Death node allows it to be converted entirely to physical damage.
it seems like harvest should have a greyed out fist next to it and that this is an unintentional inconsistency.