Registered professional shotacon here:
Most character height charts determine "Medium male" characters at an average height of 5'4 or 163cm. Each chart varies by one or two inches per character, but they seem to be in similar ranges.
Anyway, according to
https://www.who.int/tools/growth-reference-data-for-5to19-years/indicators/height-for-age 163cm is the median height of 14 years old boys, therefore making "medium male" characters young teenagers physical wise and *in my opinion* fit for the title of "shota" (but just barely since at that age they are transitioning from boys to young men).
Regardless of their actual height, their body proportions are too short and child-looking to be considered "twinks". That title would go for "tall male" characters like Kaveh and Childe who clearly have the body of slim men in their early 20s, a common description of "twinks".
