Why changing of puppies to dog is not called metamorphosis?

The term "metamorphosis" refers specifically to a biological process in which an organism undergoes a significant and often abrupt change in form or structure, such as a caterpillar transforming into a butterfly. In contrast, the growth of a puppy into a dog is a gradual developmental process involving growth and maturation, rather than a dramatic change in body structure. This process is more accurately described as growth or development rather than metamorphosis.