The latest standard I know of is SuS 2018, which I have the docs for, and does not include either switch. I searched around a bit and it doesn't seem like there is a new one. Are you referring to some draft? I sure wish this was true.
That being said, I would interpret "-exec printf '%s\0' {} +" as being a posix compliant way for find to output null delimited files. I say this since the docs for the octal escape for printf allows zero digits. However, most posix tools operate on "text" input "files", which are defined as not having null characters. Thus I don't think outputting nulls could be easily used in a posix complaint way. In practice, I would expect many posix implementations to also not handle nulls well because C uses null to mean end of string, so lots of C library calls for dealing with strings will not correctly deal with null characters.
That being said, I would interpret "-exec printf '%s\0' {} +" as being a posix compliant way for find to output null delimited files. I say this since the docs for the octal escape for printf allows zero digits. However, most posix tools operate on "text" input "files", which are defined as not having null characters. Thus I don't think outputting nulls could be easily used in a posix complaint way. In practice, I would expect many posix implementations to also not handle nulls well because C uses null to mean end of string, so lots of C library calls for dealing with strings will not correctly deal with null characters.