IME when I flew on AA issued but QR operated flights (ie 001 not 157 tickets), I had no issue accessing AS. The issue with codeshares most people have is when they’re flying on QR issued but codeshare partner operated flights. The general rule of thumb is if your next flight is a QR operated flight in business, irregardless of how the ticket was issued (ie codeshare, upgrade, light fare), as a plat you will have access.