He is good, but really
There are only two great things about him that makes him "exceptional".
He is really good when it comes to perspective
He doesn't use construction
I don't think that he is some magical genius, it's just his way of drawing takes more time to learn, cause it's more effective to just, you know, use constructions.
There are also plenty of artist who are great when it comes to perspective.
Other than that, his lines are jaggy, they look like rough sketch, not finished drawing.
If not for live performance, i doubt people would really care that much.
Though I still admire him.