If we watch a skier going down an average difficulty ski run and see that he has no problems with it, we conclude that he is a competent skier. His skills are good enough to meet the demands of that ski run. He is no novice, but is he a proficient skier? Only when we watch him ski down an expert-level ski run are we able to determine if his skills are truly proficient.
The lack of complexity in some medical visits simply doesn't allow care providers to demonstrate (and observers to observe) a proficient level of family interviewing skills. For example, a simple visit for an acute respiratory illness with only one patient in the room is a much easier "ski run" than a visit for a patient with multiple chronic medical and psychosocial problems and three family members present, each with differing opinions on the patient's diagnoses and treatments.