Well here is why I think it's not a great idea, for me anyway. The trigger pull is just the very end of the fight usually. There's a lot of maneuvering that happens prior to the trigger pull, and that's the important stuff that gets you to that point. Those are the parts of the fight that you want to study. If you're only seeing the shooting, you're missing the critical points in the fight to learn from and the most important tools for learning about the acm. Also, sometimes I really get my butt handed to me, and never get a shot off. At those times I want to see what the guy did that chumped me so badly, and that simply wouldn't be available to if the film only started when the trigger was pulled.