Is not a "no true Scotsman" situation.

USSR itself did acknowledge that whatever they have is not communism. Because they knew the definition, they knew that it's a utopian society which, as you mentioned, doesn't use money

The rest of the world had to name this regime somehow. Since there was only one party, the communist party, the west named the regime "communism".

Now we have a word with different meanings, depending to whom you speak. Certainly makes discussions between ex-ussr people and americans hard. I remember how my school teacher got irritated when we asked her "how was the life under communism". "We never lived under it, we lived under socialism" she said

To sum up, this is not a "no true Scotsman" situation, since the observing part of the world decided to extend the meaning

Ok, so you're telling me Marxist socialists propagate an idea that they have no idea how to accomplish?

I mean, I knew that, but the idea that someone would tell me this in defense of Marxist socialism by being pedantic over linguistics is kind of wild.

Your school teacher got irritated and deflected immediately rather than using this as an educational opportunity. This type of behavior clearly doesn't radiate fondness of that time. Those kids know nothing, which is why their question was "wrong". They have to pull the right levers to get answers from the teacher, as if this was some kind of unpleasant interrogation.