Or it could just be, as is often the case with US-based travel agents, that a ticket can be cancelled, but rather than getting the money back it is refunded as a flight credit that has to be used within a year and/or subject to other requirements (another one here being: has to be used on the same airline).

Given that the OP apparently no longer needs to travel on AA, they may just be questioning - given the "codeshares are acceptable" line - that they can "trick" the system into booking on a different airline, in a context far removed from the original ticket.