That’s not how they measure their success rate though. False positives don’t count against them. It’s as if you ate at a place that brought you nine wrong orders in addition to the correct one; the only problem as far as you were concerned would be if they charged you for all of them, or took nine times as long to deliver what you wanted.
Which the NSA should consider a problem, because all the energy they use on the wrong targets is energy they should be using on the right ones. But it’s not like they’re hurting for funding, so wastefulness isn’t a big issue.