It's 100% true that the child and working-age population shrinks long before the absolute population starts to dip, and in many ways that's more meaningful.
In fact, shrinking population is further deferred by improving health and longevity.
This means that many countries which seemingly stable population are in fact growing older and older, leading to an eventual cliff.
Also, title should be changed. This is "Population decline projections for 2050".
It's 100% true that the child and working-age population shrinks long before the absolute population starts to dip, and in many ways that's more meaningful.