I had heard this, this AM, and from what I could tell from the explanation is this:
Someone who was "TRULY ASYMPTOMATIC" while having the Virus was Very Rare and IF they were "TRULY ASYMPTOMATIC" their Viral Load would be very small, therefore making it difficult\harder to pass the Virus along.
It seemed to hinge on the Definition of "TRULY ASYMPTOMATIC". This would be someone who had no symptoms manifest, no fever (perceived or not), Lowered Lung Function (PulseOyx), etc...
I'm not passing this along as gospel.... My interpretation of their explanation.