Why updating a Grade code not effective dated transaction

Our client is asking why the grade code is not treated as an effective-dated transaction. They updated the grade, including changes to the grade name and code. However, they noticed that in the history section, the new effective-dated row only displayed the changes related to the grade name, while the grade code change was not tracked. Even though the new grade code was updated across the entire table, from the initial record created on 1/1/1951 through to the new updated effective-dated row, the change was not reflected in the history. As a result, they were unable to track the previous