"Whiteness" is a US concept, which doesn't make much sense in a German context. That sentence only tells me that some South Asians are neither white nor black.
I have no idea how they'd classify e.g. Turks. I think Greeks are considered white in the US, so maybe Turks too.
The other big immigrant group in Germany are Vietnamese, but they're kind of hamstrung by mostly having moved to East Germany. (East Germans in general are economically disadvantaged.)
I think statistics about ethnicity would be more useful if they were based on easily interpretable categories like own country of birth, country of birth of parents, grandparents, etc.