Govt raises prospect of new laws for COVID contact tracing app - Security - Software - Strategy

Correct. They aren't suggesting it only notices after 15 mins, with BLE there's zero reason to poll or so infrequently. I think deedee as assuming this is to save battery. In fact they are just trying to avoid stupidly large amounts of contact data for only fleeting contacts. (although you could probably argue that 15 mins is too long, would have thought 2-3 mins at most would be enough to eliminate the 'background noise')