1. The Chinese and Iranians (and maybe a couple of DU's chicken wire and cinder blocks brigade?) are claiming it's a US-developed bio-weapon. Disproving slander matters.
2. Without the context of origin, China's month of lying to the world, directly and through its running dog WHO, lacks context.
3. If the origin was the Wuhan virology lab (or other problem areas in China), being certain of that strengthens international pressure on China to clean up their act.