This tag is to be used if the appearance of the protagonist ONLY is different from their actual age. This tag can be used to describe the protagonist of a cultivation novel who doesn’t age despite being very old, though it is not recommended as it can become a very generic tag. Best to use this tag only if the fact that the appearance is different from actual age is actually used in the story.
Please note that the age mentioned is physical age, and NOT mental age. That might come under the Mature Protagonist tag.