I understand your presentation but the requirement is to record premium freight regardless of who incurs the cost. The theory is that even in the case of the supplier accepting all the charges, the cost of that premium will be included in the suppliers cost of doing business which will ultimately effect the price charged. There is a potential for hidden cost which the requirement seeks to identify and use in cost analysis.
Having said that, the requirement is to have a method to monitor the supplier performance. Because records of premium freight are mentioned in the following sentence, it is assumed premium freight is to be included in the monitoring method when applicable. As collection of these records is not specifically required (only retention of records), it is inferred that only KNOWN records are included. In other words, when the supplier provides you with this information, you are required to have records and to use them in the monitoring system. There is no requirement for you to hound a supplier for premium freight costs paid by the supplier. If you don't know about them, you don't have to keep a record of them. There may be reasons why you SHOULD know about them but that is business common sense and we are only talking about requirements at the moment.
It should go without saying, if the supplier incurred premium freight is charged back to you, this is a completely different kettle of fish and the costs should obviously be recorded, tracked, analyzed, reduced and whatever else you do when you are overcharged.
JMHO
Dave