> The UNIX 03 Product Standard is the mark for systems conforming to Version 3 of the Single UNIX Specification. It is a significantly enhanced version of the UNIX 98 Product Standard. The mandatory enhancements include alignment with ISO/IEC 9989:1999 C Programming Language, IEEE Std 1003.1-2001 and ISO/IEC 9945:2002. This Product Standard includes the following mandatory Product Standards: Internationalized System Calls and Libraries Extended V3,Commands and Utilities V4, C Language V2, and Internationalized Terminal Interfaces.
E.g. /bin/sh is from an ancient version of bash while the default /bin/zsh is not POSIX standard (without some manual mucking around at least which can break your setup if you do globally). The POSIX certificate doesn't make those less ancient or more standard it just makes the environment POSIX certified.
In that regard the stuff I mentioned in the comment is what I was referring to as standard. No 20 year old document to reference or certificate on file but I'd bet more people here are interested in things like how docker or package managers compare between systems than knowing df on macOS is certified to report in 512 byte blocks by default. I forget who said it but "the nice thing about standards is that you have so many to choose from". If you're expecting the GNU awk which has been on every machine you've ever used it doesn't matter you have POSIX awk, it's not the relevant standard to check.
Define "standard" and "non-standard", given macOS is POSIX-certified to the UNIX 03 Product Standard:
* https://www.opengroup.org/openbrand/register/brand3683.htm
* https://www.opengroup.org/openbrand/register/brand3688.htm
> The UNIX 03 Product Standard is the mark for systems conforming to Version 3 of the Single UNIX Specification. It is a significantly enhanced version of the UNIX 98 Product Standard. The mandatory enhancements include alignment with ISO/IEC 9989:1999 C Programming Language, IEEE Std 1003.1-2001 and ISO/IEC 9945:2002. This Product Standard includes the following mandatory Product Standards: Internationalized System Calls and Libraries Extended V3,Commands and Utilities V4, C Language V2, and Internationalized Terminal Interfaces.
* https://www.opengroup.org/openbrand/register/xym0.htm
Not meeting your expectations ≠ non-standard. :)