Q, as I wrote I did not watch those TV features myself. Of course the singers were supposed to represent ethnicities of the former USSR, many of which had typical facial features differing from those considered typical of Russians. The differences can be more marked than between Anglo-Saxon and Hispanic Americans, and thus sufficient for racist attitudes.

The propaganda trick I was referring to is to suggest that nationalists overcome racism and are thus morally superior.

(I just looked for samples on YouTube and found nothing perfect, but a lot of similar productions. Most are newer than 1970, when the propaganda was much softer and more subtle. If you are really interested: I think there are Mudcatters with more Soviet experience and knowledge than I have. I remember a "GUEST,Volgodon", there must be others.)