In fact, measuring targeteddumping can be achieved by resorting to the exceptional method and allowing zeroing for only the targeted groups, while using the normal, average-to-average method without zeroing for all other comparisons.
The justification for the exception under Article 2.4.2 is, presumably, that that comparison methodology allows the authorities to home in on targeteddumping, which may be revealed by patterns of price differences among purchasers, regions or time periods.