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.
That might very well be a factor in why they increased the Reference Group cohort to 18-29. Small sample sizes challenge all the Anova programs, of course.
18-29 is legitimately meaningful, if they have samples. But some will be vaxed.