I'm 99% sure the GTD needs GTI front flaps and regular Golf rears (due to rear diffuser on GTD resembling that of lower Golfs). Someone else may confirm.
That was my understanding as well.
GTI & GTD use the same front flaps.
GTI has a specific shaped cut out in the rear flaps to fit round the diffuser.
GTD can use the 'normal' rear flaps that the non-GTIs use.