He may not use them alot but other trainers using that type of training might. Though I've seen him use a prong collar and a choke chain, as I have mentioned before. Tried to find a video of it but couldn't. One thing my lecturer told us to do was to watch the show with the sound off and watch the dogs body language. To be honest, I used to like his methods! But we were told to do our behaviour modification assignments only using positive reinforcement methods.
Positive reinforcement methods are useful for problem behaviours. If a dogs got aggression towards other dogs, usually fear, I'd start off with another dog far enough away that the dog doesn't react, and reward them for being calm, then gradually bring the other dog towards them, rewarding for being calm. There's loads of ways to involve positive reinforcement in training problem behaviours. Just with aggression, it depends on the type of aggression.