Certainly it's a different era and time period but growing up in Waikiki when you were in your early teens, the north shore or Makaha were the next areas to explore. Haleiwa and Chun's were easily doable up to six feet with an eight foot set washing through and dragging you around through the white water some and giving you the jitters most certainly.
If ones confidence was on a high point, you would take a paddle out and look at the conditions for Laniakea or Sunset Beach, but no sitting on the inside to pick off some scraps. You either committed or went back to the beach and thought about it for another day.
Makaha, on a 4 to 6 foot day was pure fun. Eight to ten was still doable but the backwash would be bigger coming back at you but still a wave that could, be rideable with two people and be fun. Ten to 12 and 15 on the sets, you hoped that you were off to the side far enough and not get swept up in the huge bowl that presented a huge face of a wave. It's just a menacing wave to me.
So maybe this young boy has "some qualities" in tackling such huge waves. Youth is on his side. Not yet, with all of his physical capabilities but .... maybe he's been in the boat or on a ski with Dad and dad's friends that do tow-ins at different locations on Maui and maybe Dad has already towed his son into 8 to 10 foot surf OR, possibly even bigger surf. (shoulder shrug here) When the kid is pulled into a huge wave, I'm very sure that every ski driver is on high alert to get to the kid if he doesn't make the wave. I'm sure that he's wearing an inflatable vest just because. If he's tow'd before, lost it and got ragdolled, then he knows that it's going to be tenfold on a much bigger wave.
Years ago, (1960's) Phil Edwards brought a young boy from San Diego. Twelve year old Peter Johnson (RIP). First time to Hawaii. First time to ride Sunset Beach and Waimea Bay and both times in quite sizable surf. 10 to 12 at Sunset and 15 to 18+ at Waimea. No leash. No ski. Taking it on the head. Peter rode sizable Haleiwa and Makaha. Good style for a small, stocky kid. He'd come up spitting and coughing with wide azz eye's but he'd paddle back out and hit it again.
I guess it's all about being prepared and "able" to take the task in hand and knowing that you had folks watching your back and ready to scoop you up in a heartbeat. I think "knowing that" alone would bring a bit more confidence to one's surfing experience. The group, along with the boy should make the call on how big a wave that he'll be comfortable with in surfing.