What's the point of Chinese Heavy Scorpions when you can just make Chu Ko Nu?

I know their niche; Chinese scorps are a lot better than regular scorps against high pierce armor units like palas, eagles, and huskarls, but are worse vs archers and other ranged units because of missing Siege Engineers so having 1 less range

But couldn't you just make Chu Ko Nu, which have the same effect? Much better than regular arbs against high pierce armor units due to having 8+6 attack instead of 6+4, but have 1 less range than arbs.

Neither of the two units complement each other's weaknesses. Onagers still completely wreck both of them. What's the point of having Rocketry effect two units that both have exactly the same purpose, especially when they already have Arbalests too?