What if they have a unique definition of 'vulnerability', much like they had a unique definition of 'collect'? As a bit of internal jargon, the NSA only considered information 'collected' when an analyst looked at it. So, they could record & store bulk data about all Americans, but still claim (with a secret wink) that they didn't intentionally "collect" data on Americans. Maybe for them, 'vulnerability' means both "…
Or they straight out lied. Wouldn't be the first time.
See, now we have complete set of possible answers! So, what does it means when NSA officially announces something? I'd say, it means nothing.