The point of 200 years together being listed is that we know that he's a liar and a conspiracy theorizing anti-semitic Nazi, so trusting his word alone on socialism makes no sense. We have every reason not to trust him and no reason to trust him, especially when he contradicts archival evidence on how prisons in the GULAG administration functioned.

As for soviet prisons, they varied quite a lot depending on severity of the crime and location, with many being pretty progressive for the time. Visitation, open air prisons, and a focus on rehabilitation was common. I already linked Russian Justice, but you should absolutely read it.