Sometimes its hard to either show someone how to execute an ACM or hard for someone to explain to you how to execute an ACM. If there was a mode where you and a trainer could fly the same plane at the same time, this could be resolved.
Currently today, you can ride with someone but only one person has control of the aircraft. If there was a trainer mode, it would be more like having a trainer in your plane ala, many 2 seat training planes.