Shared everything with me and others warned me that it was not my job to hear nor handle everything.
I think one reason that A's need a sponsor is because A's usually don't except personal responsibilty that well, so if their significant other is " calling them on BS" then it just leads to arguments. However, if a sponsor pulls the BS flag, the A will likely respond better.
When my AH had a relapse, he blamed me. His sponsor quickly made him "own" his relapse as ONLY his own doing/choice....and that I was not to be blamed. If I had told him that he wouldn't have believed it or accepted it.