The Rust developers have not read the original coreutils, because they want to replace the GPL license, so they want to be able to say that their code is not derived from the original coreutils.

For a project of this kind, this seems a rather stupid choice and it is enough to make hard to trust the rewritten tools.

Even supposing that replacing the GPL license were an acceptable goal, that would make sense only for a library, not for executable applications. For executable applications it makes sense to not want GPL only when you want to extract parts of them and insert them into other programs.