South Korea has run 109,591 people to confirm 5,328 cases. I'm not sure I buy your argument.
That's good, and as more testing is done the data will reach a statistical confidence interval. Right now there is still heavy statistical bias towards testing being done on those hospitalized.
Interestingly, in China, outside of Wuhan — the city at the epicenter of the outbreak, the death rate is ~ 0.7%. Similarly, a study released by China's Center for Disease Control last month, found that if you factor out all the data from Hubei province, where Wuhan is located, the fatality rate in the rest of China drops to 0.4%.
"Abstract: From 29 January to 15 February 2020, a total of 565 Japanese citizens were evacuated from Wuhan, China on three chartered flights. All passengers were screened upon arrival in Japan for symptoms consistent with novel coronavirus (2019-nCoV) infection and tested for presence of the virus. Assuming that the mean detection window of the virus can be informed by the mean serial interval (estimated at 7.5 days), the ascertainment rate of infection was estimated at 9.2% (95% confidence interval: 5.0, 20.0). This indicates that the incidence of infection in Wuhan can be estimated at 20,767 infected individuals, including those with asymptomatic and mildly symptomatic infections. The infection fatality risk (IFR)—
the actual risk of death among all infected individuals—is therefore 0.3% to 0.6%, which may be comparable to Asian influenza pandemic of 1957–1958."
All of this is to say, the actual mortality rate is very hard to determine this early on.