I also think “GNU+Linux” is a terrible name and a worse marketing move, but you might misunderstand what it’s about. There’s no “GNU license”, and nobody ever proposed calling the system “GPL+Linux”. GNU sees itself as a project to replace the entirety Unix (hence the name, GNU’s Not Unix). A kernel is one part of the full OS, so if you combine the Linux kernel with the rest of GNU’s OS, according to this logic you get GNU+Linux. (Or maybe it should be GNU-Hurd+Linux, or GNU=~s/Hurd/Linux/... it's terrible.)
Sure, it’s not “MIT+”, but coreutils is one of the main GNU things. If you replace it with a non-GNU version, a non-GNU libc (musl), non-GNU binutils (llvm), etc, you could imagine a usable Linux distribution that would be inaccurate to call “GNU/Linux.”
No need to imagine; Alpine Linux exists today and IMO isn't GNU/Linux (I don't know what their default compiler chain is, but Alpine is musl libc and busybox for coreutils, so you can easily have an Alpine system without GNU components).
