It's different with working collies. Yes it's of course optimal for the handler and collie to be trained together but it's often not practical, so it's extremely common for farmers to send their young dogs away for training.
Yes collies bond with their handlers, but it's unusual for a young collie to refuse to work at all for a person, especially a professional trainer. They just work much better with you, as a team, when they bond with you. (And an older dog that's only ever had one handler may simply not even register that another person is even giving them commands / advice! But a young dog won't be in that situation.)
"Discipline" is something you would only do if every other possibility has failed, and only then if you are very experienced and know exactly what to do and when. Disciplining a collie while it's working is more likely to make one of two things happen; most likely is that it simply won't work again, possibly ever, and second most likely is that it increases its anxiety so much that it grips harder and more frequently.
Derek did give Skip some correction for me, exactly one time and exactly as it was needed. But Skip was already 2 years old, had had a number of jobs and handlers, had developed some habits which needed to be changed, and my verbal, "I mean it, listen to me now" noise wasn't strong enough, so Derek reinforced it for me just that one time.
You shouldn't ever need to do that with a young dog, correctly trained.