almost no smaller/newer language is added to official repo so i don't know what are you taking about it is kinda expected? (even if this languages are fully supported on linux)
Be that as it may, the initial claim was "Swift only supports a small number of linux systems" which you tried to refute but moved the goal post from "supports" to "runs". One of them are true for Swift + Arch, yes.
Supporting languages isn't the arch maintainers job I srsly don't understand your argument if all language stuff (LSP, language, debbuger etc.) work on every linux distro without any modifications is this distro "supported"?
If rustup will be removed from official repo we can argue that rust isn't supported in arch?
Notice the [AUR] tag, that means it's in the Arch User Repository, not in the official repository.
https://wiki.archlinux.org/title/Arch_User_Repository
https://wiki.archlinux.org/title/Official_repositories
Slightly ironic given the whole "confidence" side-note you made earlier...