Catalyzes the reduction of the keto moiety of phthiodiolone dimycocerosates (DIM B) and glycosylated phenolphthiodiolone dimycocerosates to form the intermediate compounds phthiotriol and glycosylated phenolphthiotriol dimycocerosates during phthiocerol dimycocerosates (DIM A) and glycosylated phenolphthiocerol dimycocerosates (PGL) biosynthesis