If you look at the data for countries where you can see a more defined peak in the curve (like China) you can see the delay in the peak of death vs reported cases.
https://www.worldometers.info/corona...country/china/
The variability of the testing delay introduces some noise (as does the change in how cases were calculated in China over a few days leading to an odd data point), but the bottom line is that there is in fact a delay between the cases that are reported and the deaths, so before we reach the peak new cases the mortality rate will look lower than it actually is and will be once the pandemic is over.
Basic data science principles.