Five days before the first symptoms the chance of a false negative with a PCR-RT test is almost 100%. On day 5 with the first symptoms a false negative can be as high as 38%. On day 8, or 3 days after the first symptoms it can be as low as 20% for a false negative.
It has nothing to do with the sensitivity of the RT-PCR tests available. Rather it's when in the infection cycle the sample is taken, and the titer of the virus in the location to be sampled.
It's estimated 35-40% of the nose swabs collected from the infected, were collected improperly, and contain no virus to detect.
There's no proof it is any more accurate than the other RT-PCR tests out there. Neither will it matter if the virus is hiding from the nose swabs.