As the author mentions in TFA, she's on the Arch staff as a package maintainer. I don't think there was a technical obstacle around the windows setup process.

https://archlinux.org/people/package-maintainers/#josie

I wonder. I sort of accidentally discovered that Rufus could edit my arm64 windows 11 install media without problem - adding a local account and bypassing the need for domain login (just as it does for amd64).

This isn't a new trick - just the regular approach to editing windows install media.

But that process still results in having Windows 11 installed on the computer. I don't think it's a stretch to assume someone on the Arch Linux staff has reasons for avoiding installing Windows which do not involve an inability to accomplish it.