Most students do turn 18 during their senior year. My birthday is in February. I turned 18 just before graduation. The cut off date when I was in school was October 15th. If you were born on the 16th, you turned 18. You were probably the oldest in your class, which was dumb. There were kids that didn't turn 18 until they were freshmen in college. The cutoff is now August 15th. My son was born in July. He didn't turn 18 until after HS graduation. Looking back I wish I would have held him back a year. Many parents are doing this now. I have commented on this many times before. Both whites and blacks.
Cade Carney has a June birthday. He was held back, so he turned 19 before going to Wake Forest. The Plumlee brothers were 16 years old as freshmen in HS! My son was 14.
It sounds like Boling has a summer birthday and his parents held him back or reclassified him. Catholic schools do that. Again, someone said I should have done that with my son, transferred him to a private school and reclassified him, but he seemed to do fine with the older kids anyway. Christian McCaffrey has a June birthday. He didn't turn 18 until he graduated HS.
If you have children and they were born in the summer, I would suggest holding them back only because so many are doing it. If everyone played by the rules, it wouldn't be such a big deal. But most people try and get an advantage where their children are concerned.