Kornet was a late bloomer physically. From the following article:
“While his classmates were going through puberty around the ninth and 10th grade, Luke's maturation process was delayed. According to his mother, Tracy, Luke's voice didn't change until he was a senior in high school. And it wasn't until college that he began growing facial hair.
"From the neck up," Frank said, "he looked like a 12-year-old."
One thing that wasn't an issue was Luke's height. He was 6'1" as a freshman in high school, 6'2" as a sophomore, 6'5" as a junior and 6'10" as a senior. Still, even though Luke was growing upward, his body wasn't filling out. His older sister, Nicole, who plays basketball at UCLA, called him a "string bean."
https://bleacherreport.com/articles/2597403-from-college-afterthought-to-nba-prospect-the-stunning-rise-of-luke-kornetConsidering his late physical development, the development of his game is likely to be on the late side too. He may have some upside with good coaching.