Dispensers with shears can harvest honeycomb from bee hives and bee nests. If honeycomb is harvested in this way and a hopper is beneath the bee hive or bee nest, the hopper only picks up one piece of honeycomb. The other two pieces of honeycomb are sprayed out randomly and are not collected by the hopper.
The attached image shows a simple redstone contraption that harvests honey and honeycomb. The dispenser on the left is filled with empty bottles, the one on the right has shears. The dispenser on the right has just harvested honeycomb. Two pieces of honeycomb have flown out and landed to the left.
The honeycomb doesn't land entirely at random. It seems to spawn in empty blocks only. A workaround is to spam hoppers beneath surrounding air blocks.