The difference between Yabu and Jimmer Fredette, Al Thornton and Shavlik Randolph is that those guys were all in the prime of their careers playing in China. Yabu's 20. We're not talking about a guy who has had years in the professional ranks to fine tune his skills. He's doing his work from instinct and athletic skills.
I'm not going to take much from those highlights beyond that he's raw but has potential. If I were Ainge, I'd want Yabu working on three things:
(1) Improving his handle to drive the lane. Yabu is too big for most SFs to guard and has good straight line speed with a quick first step. His ability to shoot 3 pointers will draw out many PFs to the perimeter. I'd want to ensure that he can put the ball on the floor and drive to the hoop while blowing by those guys.
(2) Rebounding positioning. Yabu doesn't get great lift but he's wide enough to take up space. I'd work with him on his positioning because if he can reliably shoot the 3 and rebound he'd have a long career just based on those two skills.
(3) Rather than just his set shot I'd love to see him able to drain 3s off the pick.
If he could improve those things, he'd have a chance to learn the defense when he got into Boston and he could really provide a spark off the bench at that point.