I think this is as a result of the confusion between *A rules for lounge access when flying in economy (based on *G status) and reciprocal lounge access for premium passengers.
To *A's credit, at least they document their policy, unlike OW, which seems to leave you at the mercy of the lounge-gorgon-of-the-day!
The policy is
Here
It basically says:
If you are flying in international F with any *A carrier, you, and a guest, can access any F lounge operated by any *A airline, or any business class lounge.
If you are flying in international J/C with any *A carrier, you (no guest) can access any
Business Class lounge of any *A carrier.
This is completely seperate from the *G lounge access rules, which only relate to lounge access if you aren't already entitled to it via your ticket (e.g. if you are flying in domestic F on UA - Grrrrrrrrr!).
Take my advice, print the above out, carry it with you, it solves lots of problems!
Ken.
"Learn, Guys!" - Post-It note attached to a software licence agreement by Crowley the Demon, prior to sending said document down to the immortal soul contract department in the depths of hell. - From Good Omens, Neil Gaiman/Terry Pratchett