Day in the life of Ivan Denisovich was published.
The premise was that people were self censoring even outside of what was being officially approved, so not really.
That book was published during Kruschiov era. Which was definitely not representative of the rest of Soviet era. Let alone that the book was peanuts compared to Gulag archipelago.
Eventually Solzhenytsin was kicked out from USSR and had to take exile in west. Do you really want to use him as an example of Soviet artistic freedom?
So, one dude did not censor himself, during a cultural warm up era, ended up being kicked out to exile. Which was a fortunate outcome due to his previous fame. Hmmm, is that an example how people were free to do whatever in USSR? :) Is that more like an example how dangerous it was to not self-censor even to well known people with support (for some time) from the ruling elite?
Hearing parents and grandparents stories... And having talked to older artsy people who did grow up before the fall of USSR... Self-censorship was the default modus operandi. Sure, few didn't do it. Most of those paid the price either in gulags in earlier years or mental asylums later.