Cost Scenario Effective Date

Customer created a cost scenario with a future dated effective date and then published the scenario before the scenario becomes effective.

Customer realized they incorrectly added cost for some items so they tried to undo the cost update a day before the scenario's effective date. Customer was unable to undo the cost update with the reason being:

You cannot unpublish this scenario because its costs or rates have already been used in a transaction.

Since the scenario is technically not effective until the next day why would the customer not be able to undo the cost update? Does it mean that there are future-dated transactions? Or does it mean that the publication date has more weight than the effective date?