On June 1 the oneworld alliance (which includes airlines like American, British Airways, Iberia, Cathay Pacific, Qantas, and more) changed its policies so that member airlines no longer had to check bags to their final destination for passengers traveling on more than one reservation on a oneworld airline.
Member airlines also wouldn’t be required to check customers in to their final destination on the second reservation, either. Airlines still can do this and I asked American Airlines about any changes to their policy.