Which also means that any BSD or Linux server would work as well (and likely be much cheaper).
Edited to add: and iMac Pros are still intel. It might not be as easy to switch as you think to ARM:
"The CIAO system depends on a number of 3rd party software packages or off-the-shelf software (OTS) and not all of these have native Apple ARM support (at the time of the release of CIAO 4.15.2). The CXC will monitor the situation."
As you point out, most of this software would run equally well on macOS, Linux, or any other Unix-like system. Where macOS really shines in my opinion is that it is well-supported by commercial software as well. With macOS you can natively run things like IRAF, Adobe’s software, and Microsoft Office all under one operating system. Linux under Windows has its issues, as does things like WINE.
My colleagues (physicists and astronomers) running Linux often run into issues when an administrator or conference requires files in one of Office’s formats. Likewise, Windows users struggle with some of the tools we use that are designed for *nix systems.
I haven’t encountered any open source package in my work that won’t compile equally well on ARM64 as x64. All of the commercial software that I use in my field is already native as well.