I feel the author is a bit tunnel visioned by what happens to happen this time. The Jiatan incident has a sample size of one, it'd be a bit short sighted to think that's the only way it could happen. You can imagine various scenarios where the defenses suggested here will not have worked.

Also I (as a nix user myself) think it's unlikely NixOS would have caught it. As evidenced by the fact that it didn't. (Yeah I realize I just said next time it might happen differently but it'd be foolish to put faith in nix without evidence).