It seems to me that, without going into Martian's essay, the DSI bump does contribute to the stealthiness of an air intake. The long intakes with S-bends used in modern fighters decrease the static pressure at the face of the engine. This increases the size and fuel consumption needed to achieve the performance needed by the aircraft. J-20 will therefore pay a lower price in air intake efficiency loss. Besides an additional twenty years of study and super-computer development this too will contribute to the efficiency of the engine installation of J-20 compared with F-22.