Video can be an effective method to dramatize and summarize the important components of both mechanics and philosophies. Unfortunately, video can also too easily descend into an endless (meaningless) discussion that a particular call was/wasn't perceived as "correct".
Video concentrating on pre-positioning, coverage, set-up, proximity, continuity of focus, viewing position and specific situational mechanic priorities( hands, possession/feet, redirection, grasping, etc.) as either benefits of, or deterrents to the call made are far more instructive than the validity of the call itself (of a play long over).
Speaking of descending. The instructor controls the training and the good ones do not let the subject matter stray too far of topic.