Where is this from? Not sure what you're looking for copying another users post with no comments of your own.

It long been the policy that tickets sold in the US are covered under the policy of the first marketing airlines policy. True even if it's a codeshare. Awards are always the operating carrier, so if first flight is AS, AS policies govern. Elite/credit card waivers are benefits of those programs, they're not part of a baggage policy. So even if the first flight is DL marketed, when you check in with HA on the return you don't get the fees waived, however you only pay what the policy of the marketing airline for first flight is.

It is indicated and it's is DOT rules that the baggage policy of the first marketing carrier governs. As noted the waivers of fees are benefits of those programs, ie the credit card, or SM elite program, they're not a part of the actual baggage policy. This is standard across all airlines in US.

Edit - OP edited their post after I posted to add comments.