Show me where I said he wasn't a good guitarist?
Fact is, yes his shredding is good, he has a good grasp of the technical aspects of a guitar, but you can never say he's a good guitarist from that one video.
You can glean an awful amount of information about someone's technique and musicality from a very short snippet of footage.
I can surmise from the video that he is an incredibly talented natural musician. I am a music teacher by profession and have taught hundreds and hundreds of kids around his age.
I teach sax/flute/clarinet, but the musicality is the same, and is easy to spot. From that one clip, he spots as top 3 of all the kids I've taught, no question. Very talented youngster.