The Key Topics Canvas Background can be used to point out PI Objectives differently than on the Team Boards or the PI Objectives Overview. Teams may not be able to formulate objectives to be reviewed during the draft plan review. It is too early to be able to formulate them into a goal and state the business value it brings instead of technical or functional description of the goal.
Instead, call and formulate objectives as key topics during the first day. That way it is perfectly ok, to look at the plan as entities, without pressure to formulate the objective with correct wording and leave the Objective with OKR thinking to second day after planning adjustments are done.
A Key Topic is a summary of what each team intends to deliver in the upcoming PI and what is the value they will produce. Key Topics may lead to a set of objectives during the planning process.