Coreutils is mostly UNIX/POSIX standard utilities which have been implemented under many closed and open source licenses for decades now. This is not where you build the GNU/Moat.
But GNU coreutils are ahead of all proprietary alternatives in both speed and features, are they not? I've personally not had the opportunity to work on AIX, or Solaris, or whatever (there are no machines like that where I live), but that's what I always read: "we got a new AIX/HP-UX/Solaris/whatever server and the first thing I did was to build GNU coreutils and replace the stock crap with it".
How do you know if the platform tools are faster\slower more featureful or less if the first thing you did is replace them?
GNU coreutils won on portability of knowledge, no need to learn how the platform's tools work when I can just roll with GNU. Which is great when you are dealing with multiple different varieties of Unix that are all slightly different. In general the base os tools where like all software that competes in the same space, it did somethings better and somethings worse.
People know that GNU tools were faster simply because the GNU versions' developers had famously optimized the hell out of them (many research papers written about this back in the day), while preexisting Unix tools didn't have that much optimization.
