Warren was doing partial rep Hammer curls. Partial anything, on any exercise, for most of the Pro's and top BB'ers seems to be their main choice. Cutler was doing cheating (moderate) Hammer curls. Another favorite of some of the top guy's. Most top level men today may write (usually ghost written) how they go by strict exercise movements. And even show than on video's doing by the book exercise, but not true in their regular gym workouts. Most lasting big gun's require hoisting big weights.
The whole point is for them to use max amount weight, any way they can, for most exercises. So you got partial and cheating rep's leading the way. Check out what may pass as a classic BB row. More of a semi bent over high pull to the gut. Which is really a great exercise, I have gotten good results with it. When using a closer curl grip the biceps are affected more, in most cases. Good luck and think heavy.