in the bullersune pic it looks more like the nollie inward tweak, just a guess from looking at the arms. As for bridens trick, if i remember correctly, there was a glitch in s1 where if you did a gesture while you were grabbing the gesutre animation would overrule the grab animation. so the legs and board would tweak as if doing the grab, but the hands would be doing the gesture instead of grabbing the board. had some fun times doing this on the mega ramp, you can do christ airs and the board will just float lol
edit: unless that same glitch works in s3, and bullersune used the "arm flapping" gesture, and just timed it really fuckin well with a melon grab.. who knows.