Several different styles? You're right: that is intriguing. I wonder why it's always associated with dragon style... It's certainly a useful move, if simple.

For those who don't know the technique, it contains a high block which folds in to the ear (so as not to push the attacking limb away) simultaneously with a step in and a punch to the floating ribs. I suppose the folding-in block does more to guide the punch to the side than to forcefully smother it. Kind of a slippery movement and, as I mentioned, simple.