More or less- Due to the amount of unusual requirements for installing on Apple hardware (such as being kicked off from macOS, to name the tip of the iceberg) the Asahi installer gets used for most (all?) distros running on Apple Silicon. https://asahilinux.org/docs/alt/policy/#installation-procedu...
edit: The minimal UEFI part of the Asahi installer specifically sets up a “normal” environment that other distros (like Nix) can use, it doesn’t actually install a full distro like Asahi Fedora
Apple makes great hardware (even more so now with their own CPUs) but I've steered clear of it simply because I run Linux. Last I checked the GPU wasn't fully supported and there were also concerns of of efficiency, that power draw is generally higher than macOS, thus the same hardware on Linux doesn't have the same benefit as with macOS.
Asahi includes a shell script that you run from macOS before installation to properly partition the storage (it’s quite involved). I guess, GP ran the script and then just booted from Nix ISO and installed to the new partition.