Super dirty. I mean, yeah, Murillo Bustamante probably did teach him from a young age to really "make sure" the ref is stopping the fight and that you've won, but, yeah, just brutal.
I did have one kimura win where I didn't feel the guy tapping, but in that case the ref just stood there like a fucking moron, didn't move, didn't say stop, literally did nothing. The ONLY reason I stopped was because my coach was SCREAMING "he's tapping, he's tapping, yeaaaaaaaahhhh". Lol. But yeah, Paul Harris has zero excuse here.