TFR doesn't account for mortality which has also continuously fallen since then. If you're not adjusting for that, then you're looking at meaningless decontextualized numbers. Obviously if people want a certain number of children and the children keep dying then they're going to need to give birth more to get the right number of children. Birthing is not a useful measure on its own because pre-adulthood dead children lead to the same impact on population growth as no children in the first place.