Catalyzes the stereospecific reduction of the C-4 keto group of dTDP-4-dehydro-6-deoxy-D-allose, leading to dTDP-6-deoxy-D-allose, an intermediate in the biosynthesis of the mycinose moiety of dihydrochalcomycin (GERI-155) antibiotic. Cannot directly reduce dTDP-4-dehydro-6-deoxyglucose, and thus acts after the epimerization step catalyzed by GerF. dTDP-6-deoxy-alpha-D-allose + NAD(+) = dTDP-4-dehydro-6-deoxy-alpha-D-allose + H(+) + NADH dTDP-6-deoxy-alpha-D-allose + NADP(+) = dTDP-4-dehydro-6-deoxy-alpha-D-allose + H(+) + NADPH Belongs to the NAD(P)-dependent epimerase/dehydratase family. Although PubMed:17053005 refers to the biosynthesis of dTDP-6-deoxy-beta-D-allose, it seems it is the alpha anomer which is produced by GerKI and involved in dihydrochalcomycin biosynthesis, as shown by the NMR analysis of this compound made in the same article.