I don't think you can reasonably expect a Thai LHBS to be familiar with the finer points of the declension of German adjectives! We know what they mean, in the same way everyone knew what Ich bin ein Berliner was trying to say. Hell, some of the biggest US companies still get it wrong with things like "Suffolk County" wherever that is, and many still haven't worked out that East Kent Goldings is a "thing" but Kent Goldings probably isn't and Styrian Goldings definitely isn't.
I would assume these are ordinary Nugget grown in Germany, which means they will have a slightly different biochemical profile. Mind you, the Germans don't exactly help matters with the way they name their new varieties.