Besides, what if they are mixed race? Those who claim to have German ethnicity certainly could be other than white.
Quite a surprising take there @DeathArrow ...
There are ethnic Germans outside of Germany. For example, Germans in Kazakhstan, they report their ethnicity as "German", despite being Kazakh citizens.
And people of German origin in Kazakhstan or other post Soviet states are referred as Russlandsdeutsche, or German Russians, not Germans.
Only far right groups insist on blood theory and ethnicity as a concept.
I know a few Germans whose ancestors were from Volga and who lived in Kazakhstan, they were able to claim German citizenship by the virtue of the state considering them of German ethnic descent (they never had German citizenship before).
I am from Kazakhstan, and the Germans who live there are pretty much Russians, yet the German state still would allow them to "return" by the virtue of their ethnicity.
Being German is akin to being Maori or Aboriginal.
For example, Volga Germans (https://en.wikipedia.org/wiki/Volga_Germans) were Russian subjects who lived outside of Germany; Baltic Germans as well.
More examples - Hungarians in Romania, Turks in Bulgaria, and so on.