The scissors leg move is real. However, it takes practices, LOTS of it on a flexible doll of same size...
It relies on momentum - speed towards the opponent AND entire co-ordination of body - legs, hands, hips to throw the opponent down as desired.
However, should the opponent be bigger size or one who practices the 'horse' stance, one's body would be left hanging around the neck & upper body, vulnerable to the opponent's hands actions - bare hands or with knife, etc.
So do not perform such a move unless one is exceptionally trained.
There are other far simpler moves to defend oneself by bringing down the opponent, even those of bigger size.
It lays within sports - Rugby or American football. Players just simply rush forward & instead of pushing the opponents body, they bend down & grab the opponents knees - the weakest part of the body, & with bending down leverage, to lift up the opponent & toss him over....