I've watched more of his matches now. So my opinion for what little it's worth.
Best BH whack in history. No doubt. He hits amazing winners with it. But very far from the best BH overall. I noticed a lot of limitations.
1. He doesn't loop all that much with it and when he does it is not much of a threat.
2. He makes a lot of short game errors with it (and in general his return of serve is a weakness, certainly his BH return of serve is crap compared to say FZD).
3. Except when he whacks those amazing winners he doesn't apply all that much pressure in rallies with his BH. He sort of hangs in there and kind of looks for an opportunity to unleash his cannon, which doesn't come in a lot of points.
I consider players with the best BHs to be players with the most versatile and consistent BHs. Some people I would put in that category are Jorgen Persson*, Kreanga, Kong Linghui, and especially ZJK. If you want to go back a lot futher, even Grubba. I think among current players if you consider the strengths vs weaknesses on the BH side, I would say that FZD, Ovtcharov, Harimoto, and without doubt other players I am forgetting would score better on that overall rating.
But that is in Feb 2020. Let's see where this guy is a few years from now. A lot of the issues I just mentioned were really easily seen in the video posted above in the match against Xu Xin. Watching people play defenders is not always the best way to judge. (Of course Xu Xin makes people look weaker, because he is Xu Xin).
Now if you are looking for an amazing video highlight BH winner hit to either side of the table and with insane pace on the ball, this guy is tops. That shot is scary. It is a great weapon. It is unique for sure. You just have to ignore all the other things that happen with his shots on that side.
* Persson had every conceivable BH shot of his day in his armory (except for chiquita). He was steady as a rock. None of it was super spectacular to watch (in contrast to Kreanga). All of it was very effective. That's why he actually became a world champion.