these tests... were really made for front loaders.
Alexander, it's not that way: the relevant CEI EN 60456 (or DIN EN since you're in Germany or IEC EN for the others but the text is the same) has separate test procedures for both front loaders, top loaders with impeller and top loaders with agitators, to test them in the most appropriate conditions and not the same way.
They are so strict in standardization that even the detergent composition is tabulated and also the way to put clothing in the machine to achieve consistent test results. (Paragraph H.5.4 for top loaders, H.3 for front loaders)
Those machines achieve such low grades because cleaning ability is indeed much worse than a horizontal axis machine, same is for the low energy efficiency as the water heating (even if done by another appliance like a separate boiler) is counted in.
Of course if electricity and water were free I'd want one to play with (maybe a vintage American one like the early Frigidaire!)