Very interesting question. My old club, had a limit on the number of dogs a person can bring out on a training day. They did this because they had a breeder that would show up every training day with a trailer full of dogs. It wasn't fair to everyone. Who owened/co-owned the dogs I don't think mattered as much as the number of dogs worked.
Now I train/work with more of a pay to play type place. We train multiple days a week and still hit a limit of dogs worked per training day. They know all about my green dog plans and seem to be on board with it.