Where L Wade is going here is that healthy teenage athletes are unlikely candidates for serious fractures not linked to trauma. Falling down the stairs, getting hit from a bad angle in football, ok, those are all obvious trauma.
We don't have the footage, so we don't know how he fell. If, say, he was above the rim and came down at a weird angle, ok, that could potentially be a sufficient trauma to fracture healthy bone.
If he just took a jump shot and then his tibia and fibula snapped, ok, that could suggest an underlying issue with the bone.
We'll find out when we find out. Hope it doesn't fuck up the kid's leg long term and he can return to playing the sport he loves.