It was important to emphasize that people who were unfamiliar with pets tended to confuse "sexual maturity" with the "complete developmental period" of an animal. They usually mixed these two concepts up and talked about them as if they were the same.
Take humans, for example.
Thirteen- or fourteen-year-olds, or even younger children, would have already reached sexual maturity. They could have an early marriage, early pregnancy, early childbirth, and also go out early in the morning to play. However, they could not be said to have grown up. They still needed the Minor Protection Law. It was not until they were the age of 18 that they were legal adults. It was then not until their early 20s that their brains and bodies finally stop developing. This marked their complete developmental period.