That makes sense, but do we have info on whether that actually happened? Who's overseeing the overseers? The only theory under which it would make sense to withhold that info I can think of are criminal investigation tactics, but there's no actual info on suspect transactions, is there?

Broadly and vaguely trusting in surveillance isn't convincing at all. The usefulness of surveillance must be weighed and re-evaluated against risks, as demonstrated by this incident.