A way to compare planned progress to actual progress is a common request. In my opinion it is a futile question and a pointless exercise. Sure, it sounds like a good thing to have, and probably not hard to get. But no one thinks it through.
It may be unavoidable if the question is associated with a claim or a dispute. Otherwise, however, it is an unnecessary complication, extra difficult work etc for a limited payoff. It is hard to get and does not yield useful information for project control. Lawyers and their consultants love working on disputes and claims because they can spend vast amounts of billable hours on useless complicated calculations whose only purpose is usually to assign blame and fault, and to generate further dispute.
You must note that if someone wants the planned % complete as at some date, it will require that the plan be a version with no progress recorded. That is, it will ideally be the early version that existed immediately before project execution started. Also, this is not a one off exercise because the comparison of planned progress with actual progress will be required at other dates during the course of project execution or at, say, typically, every status date.