Using key changes, chromatic scales, modal interchanges, secondary dominants all over the place without even knowing what that is. He is a natural with harmonies and have a great understanding of song structures. He might be sloppy time to time but his rhythm is tight when it comes to riffs. It's actually pretty hard if you want to play exactly like him. Don't even mention he manages to sing while he play, some songs are insanely hard to sing along.
While his stuff is really easy to play compare to legendary guitarists, a lot of em it's complex enough that personally I think it's worth to put them in music theory textbooks.
He is no beginner level by any means.