This is true, its the infamous "Fifth point" on many different IDs (they had a system internal passports to keep people in check). It was really easy for any official to discriminate if he wanted to and hard not to when its the policy.

The USSR wasn't "politically correct" in the modern Western view of the word. The party line and the state policies were fact in fact sometimes wildly discriminatory.

Those ethnic issues are a big reason USSR broke up.