"runs" would be different than "supports". AFAIK, there still isn't an official package for Swift in the Arch package registry, so to say Swift is supported by Arch sounds like "writing false information with such a confidence".
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...
https://wiki.archlinux.org/title/MATLAB https://wiki.archlinux.org/title/Scala etc.
If rustup will be removed from official repo we can argue that rust isn't supported in arch?