It is important to know who's doing what in a single pilot operation and for that person to be fully self briefed however, the CAA discourages a multi-crew culture in single pilot operations as it has been a contributory factor in a number of single pilot light aircraft accidents where more than one pilot was on board.
As such instructors are advised when briefing students to use the terms "you will" or "I will" instead of "we will".
VFE.