IIRC the evidence was blood which appeared on the carpet next to blood on the top of the duvet. If there ever was a photo of "a dissected line of blood" then I did not see it. Was there blood under that part of the duvet?
I don`t know if there was blood under the duvet but the point of the evidence is that there was a clear line of blood across the corner of the duvet and onto the carpet. Your wording of `blood ... on the carpet next to blood on top of the duvet` is downplaying its significance. Is that deliberate? It was a line of blood droplets which continued, unbroken, across the two separate items, strongly suggesting that they were together when the blood dripped there. This is the duvet that Pistorius insisted was on the bed. So how did that come to be, unless he was lying when he stated, unequivocally, that the duvet was never on the floor?