That book was quite literally written by the KGB [0], and his (ex-)wife had KGB ties [1].
From [1]:
>In 1974, shortly before The Gulag Archipelago was due to appear, Natalya Reshetovskaya was recruited by the KGB to try and persuade Solzhenitsyn not to publish.
That's all according to a defector (which brings us back to the original conversation) and a member of MI5. The notes that form the basis of those claims are still classified.
I was born in USSR, and lived in it enough to be able to reassure you it was not possible to publish a book there in 1974 just because you decided it for yourself. Even authors of fairytales were forced to make ideological "corrections", not to mention anything even distantly political.
https://en.wikipedia.org/wiki/Christopher_Andrew_(historian)