So what's the difference between flipping the hands and a flip release? I've always associated the two.
Anyway, I took a look at a few other slo mo videos of Sergeo. I can now understand why you regard it as a flip release. There's a sense of an independant club motion in there. A rotation component that isn't fully backed up by the arms swing. Sign of a chicken wing through impact, almost if he is tempoary shortening his left arm to take up the slack from a flip. I didn't expext to see that. I didn't see it on the first video I examined either.
It looks flippy face on (6 o'clock). And also from slightly behind ( 7.30). But from 4.30 it doesn't look like a flip.
Too me serge releases right wrist bend late like couples. They do it in a way that causes the face to layback and not roll. You can find pics of hogan like that too.