It just does not seem to happen and for a very practical reason - the clinician is there to sell you on going to clinics and make you feel god about your dog and training. If you don't have a "feel good" experience you either won't return or won't recommend the clinician.
The last clinic I went to tested this theory. Norm Close was the clinician and he is a very nice guy and a very good trainer. I took my Maggie - who I love dearly - but she just does not have it as a sheep dog. I tried for a long time to get her to drive and at times it seemed we would have breakthroughs only to regress. By the time of the clinic she had just about decided to shut down. I tried to send her on an outrun (usually something she enjoyed) and she simply did not want to go.
I could see it in Norm's face but still he did not say anything bad or discouraging. But I knew. And I knew I had a different dog along that showed the difference.
When I brought Piper out and told Norm this would be a different experience I could see the doubt in his face. But he was too polite and too good a salesman to say anything.
When I gave her an away command she took off like a rocket and Norm turned to me. I could see it in his face. You were right - this is a different dog. Now she still has problems but the difference was obvious.
I bring this up now as I have a number of friends coming back from clinics both near and far over the last few months. Invariably they have similar things to say. Mr. (insert famous name) loved my dogs and we learned a lot. Some of them have even come back from clinics with new dogs they purchased from the clinician he loved the dog they brought so well. And when I ask what they learned at the clinic it is usually something Jennifer has been trying to beat into my thick skull (sometimes successfully - sometimes not) for months.
My own view has evolved. I think clinics can be helpful. But I think investment of time and money in regular sessions with a qualified trainer is much more valuable and will lead to more permanent progress. Unfortunately, there are no quick fixes in this sheepdog training effort.