Good discussion! I absolutely do believe that a poorly timed yes will confuse the dog – was it the nose touch, the sniff, the paw up or the head turn that got the “yes”? Hunter is VERY operant, so he will throw a ton of behaviors at me if he thinks it is going to gain a cookie.
So, how about the “yes” that comes from your coach/training partner/judge? Do you think that affects your dog at all?