The CDC and the WHO did know that when estimating a mortality rate for a virus that asymptomatic and non-reported cases should be taken into account as is done with influenza

That's not in dispute, so please stop citing it as evidence of anything.

The point is it was not known what numeric value the mortality rate was. None of the data coming out of China was good and the numbers from Italy looked very bad indeed for known cases.

In the absence of reliable data, it could be anything. That's a fact about viruses. This is an ongoing concern by medical experts- a novel virus with a high mortality rate.

You can argue that the world over reacted. You can't compose an argument that the CDC knew what the mortality was or was likely to be.

The numbers I cite are the confirmed cases- the numbers we know are true. We also know the real mortality rate is likely less, but no one knows how much less. It also could have been worse, with people dying of an unidentified effect of the virus such as heart attacks- which has been observed in yong people - which was not however ascriobed to the virus.

So it was possible the real mortality rate could have been higher.

We still don't know.