Darwinarm64/refmt.exe has wrong cpu type

I am trying to build rescript from source. It looks like refmt.exe in the darwinarm64 directory is actually x86_64:

% file darwinarm64/refmt.exe 
darwinarm64/refmt.exe: Mach-O 64-bit executable x86_64

Is this on purpose (maybe there is difficulty porting refmt) or by accident?

Yes, it is intentional. We plan to retire refmt (i.e, the ReasonML syntax support) gradually.