Race as Culture in the USSR and South Africa

I have recently been reading about the ideological justification of apartheid in South Africa post-1948. It is almost identical to the ideological justification of Soviet nationality policies under Stalin. Never is there reference to genetics or biology rather instead both the South Africans and Soviets both always referred to ethnicity or nationality and culture. But, both viewed the concepts in ways that were completely essentialist. Primordial ethnicity and social-cultural categories rather than genetics or biology formed the basis of both systems. Somebody of German heritage in the USSR could never become Russian and after 1941 could never get the same civil rights as an ethnic Russian. He belonged to a racialized category just as much as Blacks did in South Africa. The lack of reference and even rejection of genetics and biological justifications for this policy were not unique to the Soviet Union. The apartheid regime in South Africa also rejected such language in favor of references to Volk (narod or natsional'nost), national groups and cultural identity. If somebody came from Mars and read  the Soviet and South African ideological justifications for their respective nationality policies side by side he would conclude they were almost identical projects. We only call one racial and one not because the USSR still has many defenders in Western academia. If one looks at the treatment of certain nationalities by Stalin during World War II in the light of these similarities it is apparent that the Soviet policies of deporting the Russian-Germans and others were in fact racist policies.