don't think we should think of frank speech between teacher and student as "confession," which perverts the notion of correction and instruction to a means of punishment and shame.
Since the Garden community was based in friendship as well as learning, I would think that a good amount of δῐᾰλεκτῐκή was permitted – and even encouraged – as opposed to a strict master-disciple dictate-and-absorb regime (ala Epictetus, maybe?). Likely a good amount of humor sprinkled in as well. (No question as to whom the “master” – as in mastery – was, of course.)