Is Arch ARM officially supported by the same team? If not, what might be the reason?
I think it's basically for the same reason as why they dropped 32-bit x86 support about 8 years ago. Not enough users. (That resulted in the unofficial Arch Linux 32 to maintain support.)
Once that’s done, then the ports can be submitted.
Look at the maintainers and contributors on the unofficial arm port. Orce this RFC gets accepted, the arm port can propose and figure out how to merge things together.
I write this from arch on arm (orange pi) thingy, btw