couldn't believe these numbers, read the link. correctness is obvious in retrospect, numbers are trivial to calculate by hand by just looking at daily data.
"Just looking at daily data" is your mistake. Essentially, it takes N days for the virus to kill, so deaths will lag confirmed cases by N days, and thus the calculated case fatality rate using this method is incorrect. This is why epidemiologists call it a "naïve esimator" (see section 3.1 in https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4540071/).
still can't believe them.