I'm MVPG (OWS) and traveling on a flight from SEA to SJO (Costa Rica) with a stop in DFW. I purchased the ticket in from AA and all the legs on the ticket are AA ticketed/operated EXCEPT for the first leg which is part of the intinerary but has an AS flight number (and is AS operated). When I checked in, the AS agent couldn't give me the boarding pass for the AA leg from DFW→SJO and told us to pick it up in DFW.

According to my reading of the rules, I should have access to the AS lounge in SEA since it's part of an international itinerary on OW airlines to a country that is not on the excluded list of AS (or AA, for that matter). The AS agent at the lounge scanned the Alasaka boarding pass, couldn't see the second leg to SFO, and refused us access to the lounge. Is this legit? Will things be different once I get a AA BP in DFW? If I was incorrectly refused access to a lounge, is there anything else I can do?