Sure, POSIX is basically Unix as standardized over several decades. Unix is 54 years old. Containers are a very recent development. POSIX is behind. But you do have the option to use containers/jails/zones, it's just not POSIX. What does any of that have to do with TFA?
I just wanted to point out that some unixoid systems (even some who are actually UNIX certified, but that's not really relevant to the issue) employ protection of temporary files stronger than what was suggested in TFA. The containers/jails/zones that you mention are an example of this.
