Yep. If all analysts would target addresses with exactly 51% confidence and no higher, and their confidence is the exact statistical probability they're foreign, that would mean 49% of targets are US citizens.
Am I missing does something, or does "threshold of 51%" sound awfully like "false positive rate of 49%"? Imagine that with a spam filter. Just wow.
The only way that makes sense is that they whitelist the people they like, and simply don't give a flying fuck about anyone else, American or otherwise. Spy first, deny it later.