It is not unlikely. Why? Because it supports our view of USSR and Stalin. But if this story was fabricated to support our view, then it doesn't add weight to our view. Moreover the possibility of a fabrication makes me want to reject all the story. The appeal to "our embassies" adds some weight though.
Undergraduate math education teach students to track all statements to axioms and definitions, because to do serious math one must be able for example to catch loops in reasoning. There is a logic term for that "circular reasoning": A->B->A. It is a fallacy from logic standpoint. And in a practice a loop can be much longer: A->B->C->...->Z->A. To catch them all mathematicians needs to know all about statements they refer in their proofs, how they can be inferred from definitions and axioms.
In a world of uncertainty "circular reasoning" is a sin also. It can lead to unlimited buildup of belief in statements in a loop, when they start to support each other. And to fight it we need to track how statements were inferred. It is "A->B" or "B->A"? Is it our knowledge of Stalin and USSR conceives the nice story in the article discussed, or the nice story is based on facts and therefore adds something to our knowledge about USSR?
But the trouble is all this tracking of sources must be done before you decided to accept story as truth, because if you decided to accept as a truth something it would be used in your reasoning afterwards. And if it was not truth, then you can get all the consequences of a false statement in your priors. It is not as bad when you reason under uncertainty as it might be if you used logic with the law of the excluded middle, but bad nevertheless. Mind works this way, any slip from truth leads to spoiled reasoning which adds even more untruths to your worldview. I personally rarely remember my night dreams, but when I do it is a disaster, because it takes some time to notice that it was just a dream and all the conclusions are continuations of the dream, so they must be tracked and purged.
You are trying to justify the claim of the article based on our understanding of Stalin's regime, and if you are successful it doesn't add anything to our understanding of Stalin's regime because if was inferred from it. In this case it is a fiction.
At the same time the appeal to "our embassies" is fundamentally different. It may be a not very convincing but it might be based on facts. It can support other claims about USSR.