Each instructor teaches their own way. it is not for me to question his training. video can assist in training but usually that is after the teaching of the kata has taken place. It is more for review. One of my instructors gave me a film of the kata that I was taught and this was used for review since, in time, we forget. This was used to help me maintain correct kata. From the video I too saw suttle differences in what I thought I originally learned and what was showing on the video. I suppose that there are a few reasons for that. As I said, usually kata is taught first and video (or still photos) were used for review...but this was as far back a 30-35 years ago. Perhaps with technology times and training methods change. I can see the advantage but I can also see a disadvantate too. I suppose it depends if you are comfortable with this form of learning. Good luck