If the manager of a user is from a different legal entity, then there should be no requirement for a exchange rate between the approvers entity and the submitters legal entity. Since the expense report is created in the legal entity of the user submitting it and the expense report is also in the accounting currency of the legal entity of the user submitting the expense report then there should not be a requirement that just to approve the expense report we need to have an exchange rate between the currency of the submitters and the approvers currency.