Age and height do not always correspond. Aside from the situation of dwarfism, it is too common to find short people in our communities who are several years old.
In my opinion, a man is a mature male who knows and performs his responsibility. That is, he works hard to fend for himself, takes care of the family, pays bills, fees, … Most importantly, he does not depend on others for survival. A boy would depend on others – parents – for survival. This is the difference.