A CRM issue here is the apparent lack of a good debrief. If the student had asked for an explanation about the Captain’s actions this should have been given together with the reasons for the decision. These may have been misunderstanding, the Captain did not see the situation in the same way as the student – more discussion as to why, the Captain may have made a mistake, or the student was mistaken. It would be disappointing for an instructor not to admit to error, but we all make mistakes and are reluctant to discuss them. Debriefing is a way of both continued learning and improving our airmanship.
If a mistake was made, was it the acceptance of an aircraft with a deficient trim indicator, an error in setting trim (student or instructor), or an error in not detecting the miss setting. Investigate how such an error could have been made, rush, hurry, oversight, poor design; all good learning points.
A debrief is a most valuable yet most underused CRM tool. Both student and instructor should remember that in aviation we never stop learning from others and particularly our own mistakes.