Yeah POSIX standardizes a bunch of tools, mostly the ones you'd expect (cut, cat, file, etc). I agree with the conservative standardization for the most part, but I selfishly would love these more niche tools to be available on a fresh box. Good point though, I just want to be a little lazier in my script writing I guess :)
I guess distros are the next layer over POSIX standard. Distributions have the ability to, mostly arbitrarily, select the default packages they ship in their releases.
I've always used this site as reference: https://pubs.opengroup.org/onlinepubs/9699919799/