Latest stable firmware is v18.104.22.168. All versions after that are non-public beta with extra languages under testing. Arabic was added in beta v22.214.171.124 and removed in beta v126.96.36.199. It was never officially supported! I'm sure Huami had its reasons for removing it.
So, until next official release, please don't ask why a "beta" language was added or removed. And after the official release, please ask Xiaomi or Huami why any language was removed, not us! Everything happens for a reason.