What's up with the cavalary bias in regional units?

[DukeOfLorraine]

On another thread I proposed the hwacha as a RU for Chinese Koreans and Mongols (future Jurchens too), which would be a unique siege unit.

New regional unit : hwacha rocket launcher

Hello, I have an idea for a regional unit for the Koreans, Chinese and Mongols : a medieval rocket launcher, also called hwacha in Korea, that would be a replacement for the onager and siege onager. Compared to the mangonel line that it replaces (as an anti-mass-infantry ranged siege unit) : Wider blast radius Fires shots by salvo (like the chu-ko-nu) instead of all at once, each shot dealing full damage Higher reload time Poor accuracy, slower projectiles Overall the unit would perform …

We were debating whether having it replace the onager and siege onager, replace the scorpion line or be added on top of them, but it looks like a good choice that could synergise well with all 3 civs bonuses and UTs.