First GNU coreutils is going to remain GPL-licensed, so nothing that already exists is being given away; the only thing that is happening is that some people have decided to write brand new code. (And it is worth noting that GPL only says that if you share the binaries, you have to share the source code; if your changes are only used internally, you do not have to contribute them back, though you probably want to do so since it makes your life easier down the road when you want to use newer version of upstream.)
Second, what scenario exactly is it that you are worried about? I want a specific and plausible answer, not just vague allusions.
Finally, if the Rust authors are fine with the possibility that someone will use their code in this way, then who are we to tell them to stop their development when we can continue to use GNU coreutils?
You did not answer my question, and I think it is an important one so I will repeat it: should they abandon the project if they are unwilling to use your preferred license?