I'm with lonetiger on this. Wing chun people have been doing this kind of training for years and now it's the only videos we ever get to see. This kind of training is so basic. If they put gloves on with headgear, and started at a distance, I bet the smaller guy would look a lot better. Chi sao, or any drills where the arms are connected, allows for safety of the people doing them. It's safe because you're only dealing with a few kinds of attacks and once you understand that you can take advantage of people who haven't learned how to deal with the same kind of attacks. Add kicks in and it won't look like this clip at all.

Have someone who does wrestling do this same drill with the teacher and it won't go that way at all.

This kind of training is good in the beginning but hinders wing chun people in the long run. Then you see wc guys trying to do the pak/jab at someone from the long range.