Oh they likely have enough samples. I’m sure there have been 18-29 yr olds who somehow inhaled a HUGE virus dose and didn’t have much of a chance.
But it’s rare. And the 85+ death is not rare. The ratio is the X number.
I studied statistics. The death rate of young children is too low to use extrapolate out to those older age groups It’s not enough of a sample.
It’s improper work, and if it’s accurate it’s by chance only.