I agree with ikevi's approach of looking at this issue through the lens of the ACA's goals as an organization.
This is less about whether an AER is verifiably a "pure" species (whatever that means) and more about the ACA's approach to aquarium (vs. wild-type) strains of fish (line bred, hybrid, or unknown) and the people who enjoy them.
Trying to approach this from a technical definition of "hybrid", "species", etc., etc. direction hasn't worked (to date) because it doesn't take into account the reality of the hobby: that a lot of people like super-naturally colorful fish (like AER...or EBJD....or fancy discus....or flowerhorns).
To me at least, to say that one "man made" fish is OK because it probably only was derrived from fish that are currently classified (by man) as a single species...and another "man made" fish is NOT OK because it was (intentionally) developed from more than one species just doesn't make sense.
Both fish are OK. They are what they are. And they're both "cichlids".