For the record, I recently found out that there are preteens who had such huge growth spurts that they could pass for late teenagers. Some female cases' breasts had enlarged so much over merely 1-2 years that they had to undergo drastic breast reduction surgeries, and the ones that didn't do the reduction early enough have had to live with lifelong malformations to their upper back bones (since they were in a delicate stage of their skeleton's growth) that force them to adopt hunched postures because straightening themselves up brings constant agony from misaligned/misshapen shoulder blades, ribs and/or vertebrae.
TL;DR oppai lolis like Nonka are actually possible in real life, fictional ones are just benefiting from the commonplace defiance of physical laws and biological constraints in manga/anime.
