I can't tell from that context if it means average stature or below average stature, but the OED lexicographers put this citation under the sense. Moderate or middling in size, stature, or age. Obs. of the word mean. All right, so the term mean stature has been used to mean of moderate or middling stature, in other words, of medium height. That sense of mean is considered obsolete, but I guess a fantasy writer might choose to use an archaic or obsolete expression on occasion.
https://scifi.stackexchange.com/questions/67345/what-does-it-mean-when-harry-is-described-as-having-a-mean-stature
Pharmaceutical companies Genentech and Eli Lilly, makers of human growth hormone, have worked to medicalize short stature by convincing the public that short stature is a disease rather than a natural variation in human height.
https://en.wikipedia.org/wiki/Short_stature
Short stature is defined as height that is two standard deviations below the mean height for age and sex (less than the 3rd percentile) or more than two standard deviations below the midparental height.4 A growth velocity disorder is defined as an abnormally slow growth rate, which may manifest as height deceleration across two major percentile lines on the growth chart.
https://www.aafp.org/afp/2008/0901/p597.html
Tall stature is defined as a height that is two standard deviations above the mean for age and sex (greater than the 95th percentile).9 Excessive growth, defined as an abnormally rapid growth velocity, could manifest as height acceleration across two major percentile lines on the growth chart.
https://www.aafp.org/afp/2008/0901/p597.html
Children and adolescents whose heights and growth velocities deviate from the normal percentiles on standard growth charts present a special challenge to physicians. Height that is less than the 3rd percentile or greater than the 97th percentile is deemed short or tall stature, respectively.
https://www.aafp.org/afp/2008/0901/p597.html
Short stature. Short stature refers to a height of a human being which is below typical. Whether a person is considered short depends on the context. Because of the lack of preciseness, there is often disagreement about the degree of shortness that should be called short. In a medical context, short stature is typically defined as an adult height that is more than two standard deviations below the mean for age and gender, which corresponds to the shortest 2.3% of individuals. In developed countries, this typic
https://en.wikipedia.org/wiki/Short_stature
So 'mean stature' means he hunches over and has a 'tough face' to him, as if hes hiding within himself. He doesn't carry himself with pride but carries himself in a rugged and reserved way. Also, I think in the 3rd book Aunt Marge says Harry has a mean and runty look about him.
https://scifi.stackexchange.com/questions/67345/what-does-it-mean-when-harry-is-described-as-having-a-mean-stature
Short stature can also be caused by the bone plates fusing at an earlier age than normal, therefore stunting growth. Normally, your bone age is the same as your biological age but for some people, it is older.
https://en.wikipedia.org/wiki/Short_stature
Mean in this case is little, or short. A bit of an archaic usage, I believe. Several places in the early Harry Potter novels describe Harry as being very short and skinny for his age. I think it might even mention explicitly that he was undersized due to his mistreatment by the Dursleys.
https://scifi.stackexchange.com/questions/67345/what-does-it-mean-when-harry-is-described-as-having-a-mean-stature
In this case, then, mean stature appears to be using mean in its adjectival sense: 3 (especially of a place) poor in quality and appearance; shabby (of a person's mental capacity or understanding) inferior; poor
https://scifi.stackexchange.com/questions/67345/what-does-it-mean-when-harry-is-described-as-having-a-mean-stature
what does in stature mean
'Mean stature' means he hunches over and has a 'tough face' to him, as if he is hiding within himself. Stature means one hunches over to another as if hes hiding within themselves.