I thought that was a groin strike and a redirect / block. For example, someone is doing a haymaker. The upper arm deals with the haymaker while at the same time, the lower arm strikes the groin. I've seen other's do it as a double palm strike. One to the face and one to the groin.
this is the video that I watched. The move is at :36. He doesn't tray to wrap his arm. Instead he turns and deflect a low kick or low punch and strikes high. Int the video that JR 137 showed he turns and deflects a high punch and strikes high. Had these guys would have done a basic Jow Ga punch had they closed the second fist instead of using a knife hand.
After seeing this video I now see the wrap at the 4:37 mark. I'm don't train in this system so this is just an uneducated opinion based on the little bit of martial arts that I know. I wouldn't try to use it as the way he shows it in the video. If I'm going to redirect a hand like that, then I wouldn't bother trying to grab it. I would simply redirect and move forward with a double palm strike, one at the face and the other towards the lower abdomen or groin. In the kata both hands go out at the same time. When I look at the kata I just assume that they are fighting multiple people
This is more of what I had in mind and it actually makes more sense to me from a Jow Ga perspective. You can see the technique in question at 2:19. The wrap around the arm is more of a redirect than a wrap. I'm not saying that one way is correct and the other way is wrong because techniques often have more than one application. This particular application may be a higher % for you