I already did. His head is above the rim right here.
If you can't tell in that gif, then here's a closer look.
I'll admit the camera angle makes it difficult to judge how much of his head is above the rim right there, but you get the point. And you can't just go by whether his head is above the rim. There are other factors to consider such as how far away from the hoop he's taking off. You can't watch a guy dunk and be like, "his head isn't above the rim!" Well, no **** bro, he took off from the FT line.
Take a look at how far away he has the ball away from the rim right here. It's unreal.
When I watch LeBron from high school, he doesn't seem any more explosive to me than Wiggins.
Wiggins high school mix:
https://www.youtube.com/watch?v=GLsK-ZoL9sY
LeBron high school mix:
https://www.youtube.com/watch?v=MHiqvzLhvn8
But if only we could KNOW what his vertical is. Maybe in the future they'll invent something that can measure and quantify such a thing.