This is exactly what I meant by "deployment problem" and "appraisal problem" in my earlier comment.

Just because a KP is holding a certain title and given certain work pieces to lead/manage/oversee, doesn't always mean that they are the primary driver of the impact of those work pieces that they are managing. It could be a TL under their charge, or a regular experienced teacher, driving most of the progress and outcomes. But if you simply look at the hierarchy at face value, then you will say oh yeah definitely more credit should be given to the Head because he is the Head. But when you go deeper it is not universally the case.

From your statement it seems like the way you will conduct appraisal is.. you only look at who is the formal leadership title holder, accord recognition to the title holder and call it a day.