> I also do sysadmin stuff from macOS

MacOS is fine as a client/dispatch node for SSH/Ansible/Terraform/whatnot; I think they meant that you cannot sysadmin MacOS itself as a target with many of the same tools/techniques you would sysadmin a Linux server.

I wish that weren't true, as someone who struggles with a lot of cross-platform Puppet tooling that I wish behaved better on Mac. No, Nix doesn't help; not when the goal is "configure other people's machines to a baseline but don't otherwise prescribe how they should use them".