Not ridiculous. After the first town in north east Italy was put in quarantine (Vo Euganeo) the local governor decided to test the whole town for Coronavirus (a few thousand people). More than half of the infected people where without symptoms.
It should be obvious, when you have a virus with an infection rate doubling X number of days and it takes X or more days to start showing symptoms, if you do a random sample, 50% will be asymptomatic. That does NOT mean that they will continue to be asymptomatic