Considering the usage of soviet now as an attributive tag, we should probably figure out whether or not we should include the Warsaw Pact members into the tag as well (East Germany, Poland, Czechoslovakia, Hungary, Romania, Bulgaria, possibly Albania).
East Germany, out of all of those, is technically the only one who wouldn't need the tag, given it only existed because of the Soviets. Following behind is Czechoslovakia, which existed before the war too, but after communism would split in two.
But for the rest, there's a tangible association between the era of communism all those countries were under with the one who put them in that era in the first place, the Soviet Union. Whether it be in architecture, technology, and to some degree, even uniforms.
If we use NNT's example of 'russia + soviet', then it would make sense to do the same for the other countries, if applicable.