Just curious, and this might sound naive but this is a serious question.

Are drone "blades" (not sure of the correct term) more efficient when they aren't enclosed? I understand this is a test unit and there are myriad safety precautions taken when testing. But my first thought when seeing open blades is what happens if it falls, trips or otherwise goes out of control? Then you have rapidly spinning blades going helter skelter to deal with. Not just hitting into any soft humans standing around. But the floor, tables, doors, wires, expensive computer equipment. It seems a bit daft unless it has a purpose that I've missed.