I'm pretty sure you are right about that and KingTriaxx is wrong.Thank you. I was under the impression that manual farms planted and harvested, but do not place blocks.
Hemp doesn't need replanting though, if you only break the top half, it will grow the top half back, and it will grow faster than if it grows from seed. So the farm is actually doing it wrong by breaking the whole plant.
Just curious though, did you try an "orchard" farm? I don't expect that to work, but it might.