Yes it is understandable because of how the Nazis exploited the PIEs in their propaganda of master race just 70-80 years ago. But let's remember that the Nazis claimed that the PIE homeland was in Germany (Central-Northern Europe), not in the Volga-Ural region.
Check this quote from the Nazi brochure for the 1938 Nuremberg Rally, about the "Proto-Indo-Germanic peoples":
So the Nazis equated "Nordic race" with Indo-Europeans, and claimed that the PIE homeland was in Central-Northern Europe.
Not quite the same as the Kurgan Hypothesis, or any other hypotheses about Baltic-Ural or Volga-Ural PIE homelands.
And also recognizing Slavs as part of "Indo-Germanic" family, did not prevent the Germans from judging them as inferiors.
When it comes to Semites, the Nazis recognized both Arabs and Jews as Semitic peoples, but only Jews as subhumans.
Do not try to find consistency or logic in Nazi ideologies, because you won't find much anyway. As for the "Nordic race":
One of Nazi Germany's anthropologists, Hans Friedrich Karl Günther (also known as Race Pope - Rassenpapst - or Race Günther - Rassengünther), who was a Nordicist not a Germanicist (a difference was that Germanicists preached the supremacy of Germanic peoples, while Nordicists preached the supremacy of "Nordic types" regardless of what language they spoke) acknowledged this in 1933:
"(...) Günther found the overwhelming majority of Germans racially mixed, just 6-8% pure Nordic and the East-Europid race, which he despised, common in the east and north ... (Günther 1933: pages 57 and 112)"
So just 5-10% of Germans could be classified as pure Nordic - a ratio probably lower than among some of Baltic and North Slavic groups. By contrast among ethnic Swedes, as many as over 30% were classifed as pure Nordic, and another 1/3 as East Baltid:
"(...) Swedish anthropologists like Nordenstreng adopted the East-Baltic, along with the Nordic, as the real races of Sweden ... (Kemilainen 1994: p. 402; Hildén 1928: pp. 220-21). Nordenstreng ... identified ... 31% ... of pure Nordics ... in Sweden ..., while Lundborg and Linders in 1926 said 36% of Swedes were East-Baltic (Kemilainen 1994: pp. 402-3)."
Based on those stats, some members of the SS started to claim, that 90% - 95% of ethnic Germans were also subhumans:
"(...) The more extreme SS men began to take Nordic supremacy to its logical conclusion that Non-Nordic Germans were inferior, and that five to ten percent of the [ethnic German] population, its best selection, would ultimately rule the rest (Ackermann 1970: page 174). Would Nazi Germany eventually have instituted a truly anthropological race discrimination system ... ? The fate of Germany's brown-haired brachycephals might ultimately have depended on Heinrich Himmler's aptitude for factional manouvering within the Nazi party. (...)"
But other Nazis tried to find excuses & solutions to the problem of incorporating 90% of "impure" Germans into the master race:
"(...) A prominent German anthropologist was accused of explaining away the numerous inconvenient Non-Nordic Germans by attributing head-shape to infants pillows (Huxley & Haddon 1935: p. 40). To absorb South Germans into an expanded Nordic race, Fritz Lenz questioned the validity of the Alpine race (Eickstedt 1934: p. 388; Lenz1936: p. 726)."
Nazis considered Non-Nordic looking Germans superior, but Nordic looking Jews (yes, such types also existed) inferior.
Quote:
"(...) Unlike scientific anthroposociological elitism, mystical, cultural Germanicism made almost all Germans into superior Aryans, even if as blond as Hitler, as dolichocephalic as Rosenberg, as tall as Goebbels, as slender as Goering, and as manly as Streicher , as an anti-Nazi joke put it (Huxley & Haddon 1935: 26). While Lenz criticised the mythical, irrational excesses of Nazi race propaganda, and Günther declared the Nordic movement will always ruthlessly reject Germanicist enthusiasm , his Nordicist rival Clauß advocated a less biological and more culturally defined northern supremacism, while Kaup led a more populist campaign for an inclusive German national race [so a race including all Christian German-speakers regardless of their anthropological traits] (Wiercinski 1962: 12; Lutzhöft 1971: 17 & 22-23; Graham 1977: 1159). (...)"
And:
"(...) Himmler [for some reason] equated former inclusion in the Holy Roman Empire with possession of the same blood as Germans (Ackermann 1970: 110). Nazis strained to be Nordicists, but within limits: Himmler, watching Jews going to the gas chamber, picked out a blond, blue-eyed boy and asked him if he were a Jew and if both his parents were Jews. When the boy answered in the affirmative, Himmler replied: What a pity, then I cannot save you. (Mosse 1978: 221). (...)"
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Source of all quotes:
http://www.friendsofsabbath.org/Further_Research/Genesis X and Origins/Races of Europe_McMahon.pdf
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This is all totally off-topic here, though...