if anyone is afraid of this happening to them, I'd recommend the deterministic nix installer. it has an atomic installation process where each step is reversible with the uninstaller. This is uniquely a macos issue since the setup is a bit different to other OS's in terms of creating a read only filesystem for the nix store, but the determinate installer was built to fix any worries of that happening.
https://github.com/DeterminateSystems/nix-installer