I have found award availability from the US to Sydney on AA. If I try to add a domestic QF flight, there's no availability, even though if search the QF flight separately, there is ample space.

An AA phone agent assured me three times that although bags won't be checked through if I book the domestic sector separately, AA will protect me if I misconnect in Sydney to that QF domestic flight. When I asked if that meant accommodating me on a later QF flight without any penalty, she said yes.

Does this sound correct? I would have thought AA would only look after me if the flights are on the one ticket.