The Anthralite Knife item added for Farmer's Delight compatibility is added to the farmersdelight:tools/knives tag, but not the forge:tools/knives tag, which Farmer's Delight uses (At least in some versions such as 1.2.7, I assume the unused tag is a leftover from an older version of Farmer's Delight) for recipes, thus making the knife unusable for crafting.