Realistically, the Posey Challengers 77+76 and the Gurney AARs didn't have their hoods painted black either... probably for marketing reasons... but those cars were factory-prepped early-on before the mass sales (few that they truly were) began for the "street" AARs and T/As. I've read it in the past as to the reason for the flat black hoods.... sounded good and logical. Painting a T/A hood and finishing it properly (such as under the scoop) would have been time consuming and rather difficult (AAR hood easier); also, the flexing of the fiberglass would only eventually display stress cracks in any paint (as well as on the flat black... which they all eventually do).. so, perhaps, another reason why MaMopar chose not to paint the hoods the body color.
When Sid Rust purchased one of the Gurney AARs and eventually ran it in the midwest GT-1 race events, he re-painted the 'Cuda a beautiful silver color (ala... silver B'Cuda fish color!) and painted the fiberglass hood and fender tops flat black, respectively... looked really cool!