ParkRxI see what you are saying in that it looks like a backflip late one but I don't think it is. I think it's a laid out under flip. He starts his his rotation slightly off axis which brings the rotation around. Versus a backflip late one starts as a completely on axis backflip that with mid air adjustments adds a 180. I know it's a small difference. Heres a clip from a king for example
https://www.instagram.com/p/B8rU_Zqj8mN/
Upvote for King Antti. A backflip late 180 is done by changing your moment of inertia in the air, while a flair/underflip is determined in the set, like other off axis rotations. Similar to how a cork is different than a full