Single modal workouts are not often programmed at many CrossFit gyms. I think this is because they do not help the individual develop a wide variety of skills like what CrossFit preaches. Instead it tests your capacity solely in one movement domain, either weightlifting, barbell, or gymnastics.
Single modal workouts are most commonly programmed with only the barbell. Some examples are the open workouts above, Grace, and Isabel. These are very effective tools for training individuals whose limitation is the barbell because it forces them to grow comfortable with it and continue to move it under fatigue. Also the loading is just heavy enough to where they must be efficient with the movement, to be able to complete all reps in timely manner.
I do not think it be wise to program single modal workouts often because of the small amount of time they are tested in competition, but from time to time they are a good measuring stick for someone trying to improve their capacity in a certain domain