I don't think your definition of "standard library" is correct. For example, there's glibc (which you might argue "ships with" GNU stuff) and then there's musl

I don't think your definition of "standard library" is correct. For example, there's glibc (which you might argue "ships with" GNU stuff) and then there's musl (https://en.wikipedia.org/wiki/Musl https://en.wikipedia.org/wiki/Musl) which is an alternative standard library for C programs.