I agree with what you say, but "Never was" is contradicted by your Wikipedia link, which shows Ukrainians in the second position at the 1926 census, being overtaken by Tatars in the more recent censuses.

However, it is not said which is the territory for the 1926 census data, it may have included a part of the present territory of Ukraine, because the borders of present Ukraine are very different from the borders of Ukraine after WWI.

Such census data about Russia and the Soviet Union are hard to interpret without precise knowledge of the corresponding territories, because the fluctuations in numbers may be unrelated to natural growth, but determined by administrative reorganizations or forced deportations.