Identify which knowledge remains relevant to the new U.S. duties and which has become historical. Do not describe an abandoned method as the continuing assignment.
Explain transition work with its actual limits
The applicant may help reconcile old and new records, but specify the tasks and expected period. Review material changes and status before assuming that a previous description authorizes the revised work. Divide the knowledge into what transfers, what expires and what becomes historical, and give each a date.
Knowledge of the categories, the drivers and the approval path usually transfers, because the questions they answer recur under any method. Knowledge of a superseded calculation expires as a working tool but remains useful for reconciling prior periods, which is a real and describable task with a beginning and an end. Hypothetical example: a group-wide standard method replaces the local one a few weeks before the transfer date, and the petition, drafted around the old method, now describes an assignment that will not occur.
Rewriting the duties honestly is the shorter path; presenting an abandoned method as the continuing work is not. Where the change is material, review it before relying on any document prepared under the earlier terms, and confirm that the description of the proposed U.S. duties still matches what the receiving entity intends the person to do on arrival.