I know what you mean Dekka. I used to use the Dunbar play, recall, collar grab method as well and did it with small groups. I often have a student with me and it still wasn't enough to prevent 'accidents'.
I just found that when there were problems...and there were, it was often too late for shy pups as well as too much practice for the overly bold pups.
I absolutely do agree with allowing puppies to play much more exuberantly and that does happen in class to, this was only a short clip and of the entire group at once. I just don't ever believe that anyone, me included, can control interaction nearly as effectively off leash even with groups as small as 4-6.
I wish that I could find Jean Donaldsons article. I know that she and Ian butt heads but I really agree much more strongly with her views. Jean has not been doing off leash play in class for several years either for the same reasons.
I have to add that the 'BY ME' command is taught and practiced in class as are many other on leash exercises and they are better, not worse because of the social experiences allowed periodically on leash. Structure is very important but so is the ability for pups to learn to have relaxed interaction on leash.