Now the actual purpose of this thread is to find a form of words that distinguishes these cases, so the docs can be patched to avoid the current inaccuracy which suggests that wantarray is never meaningful at the top level.

The docs say nothing of whether wantarray it is "meaningful" or not at the top level. All they say is that its behavior at the top level is officially unspecified. I.e. two different releases of Perl may exhibit different behaviors and both be within spec.