https://bugs.winehq.org/show_bug.cgi?id=47674
--- Comment #3 from Ken Thomases ken@codeweavers.com --- The issue is that the Mac C libraries only have a fairly narrow selection of installed locales. In particular, it doesn't support Arabic locales. I don't know if it's possible to install third-party ones.
There's much wider support for locales in the higher-level libraries and frameworks, which is what most Mac software uses.
Because Wine uses the C library's locale functionality to query the locale, it's not understanding ar_SA.UTF-8 and falling back on the C locale (albeit with UTF-8 character encoding). Wine doesn't rely much on the C library's locale functionality other than detecting the system locale settings, though. So, if you configure it with the desired locale in other ways, things should work.
In particular, there's drive_c/windows/win.ini in the prefix and the registry settings under [HKEY_CURRENT_USER\Control Panel\International]. Try configuring those for Saudi Arabia/Arabic.